Welcome to TNPSC Physics Force Test 4 – Friction Free Online Test! This quiz covers important Friction TNPSC Questions based on the TNPSC General Science syllabus. Test your understanding of the types of friction, factors affecting friction, and the advantages and disadvantages of friction. You’ll also revise practical applications of friction, including lubrication and rolling friction. Answer these MCQs with explanations to strengthen your Physics concepts and prepare for the TNPSC examination.
Note: Detailed explanations are given below this Free Online test so you can learn from each question and build stronger knowledge for TNPSC exams.
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TNPSC Physics Force Test 4: Friction – What You Need to Know
This section provides detailed explanations of friction to help you understand the concepts behind the questions in this Free Online Test of TNPSC Physics Force Test 4. Learn about the different types of friction, factors affecting friction, and the advantages and disadvantages of friction in everyday life. It also explains the importance of lubrication, rolling friction, and practical applications of friction with clear examples. These concept notes will help you understand the subject more easily, remember important points, and improve your confidence in answering Friction TNPSC Questions for TNPSC General Science preparation.
1. Friction is a force that:
Correct Answer: A. Opposes relative motion between surfaces in contact
Explanation: Friction is a force that opposes the relative motion or the tendency of relative motion between two surfaces in contact. It acts in a direction opposite to the motion or the tendency of motion between the surfaces. Friction is caused by the microscopic irregularities present on the surfaces, which interact when they come into contact. The amount of friction depends on factors such as the nature of the surfaces and how strongly they are pressed together. Friction can act even when an object is stationary. For example, static friction prevents an object from starting to move when a force is applied but is not strong enough to overcome friction.
Real-Life Examples:
- Walking: Friction between our feet and the ground helps us walk without slipping.
- Bicycle brakes: Friction between the brake pads and the wheel helps slow down and stop the bicycle.
- Pushing a box: Friction between the box and the floor opposes the movement of the box.
- Writing: Friction between a pencil and paper allows us to write.
Why the other options are incorrect:
- B. Increases the mass of a body: Incorrect because friction is a force and does not increase the mass of an object.
- C. Acts only on moving bodies: Incorrect because friction can also act on stationary objects. Static friction prevents an object from moving when an applied force is insufficient to overcome it.
- D. Acts only in liquids: Incorrect because friction occurs between solid surfaces and also in fluids, such as liquids and gases. For example, air resistance acts on a moving bicycle.
2. Which type of friction acts between two surfaces that are in contact but not moving relative to each other?
Correct Answer: B. Static friction
Explanation: Static friction is the force that prevents two surfaces in contact from sliding over each other when an external force tries to move them. It acts when the surfaces remain at rest relative to each other. Static friction adjusts its value according to the applied force, up to a maximum limit. When the applied force exceeds this limit, the object starts sliding, and sliding friction acts.
Real-Life Examples:
- Pushing a cupboard: When you push a cupboard gently and it does not move, static friction between the cupboard and the floor prevents it from sliding.
- Walking: Static friction between your feet and the ground helps prevent your feet from slipping.
- A box on the floor: When you push a box gently but it remains stationary, static friction balances the applied force.
Why the other options are incorrect:
- A. Sliding friction: Acts when one surface slides over another.
- C. Rolling friction: Acts when an object rolls over a surface, such as a wheel rolling on a road.
- D. Fluid friction: Acts when an object moves through a fluid, such as air or water.
3. Which type of friction acts when one surface slides over another?
Correct Answer: C. Sliding friction
Explanation: Sliding friction is the force that opposes the motion when one surface slides over another surface. It acts in the direction opposite to the sliding motion. It occurs because the microscopic irregularities of the surfaces interact with each other. The amount of sliding friction depends on the nature of the surfaces and how strongly they are pressed together. Sliding friction is generally less than the maximum static friction and greater than rolling friction under comparable conditions.
Real-Life Examples:
- Pushing a book: When you push a book across a table, sliding friction acts between the book and the table.
- Dragging a box: When a box slides across the floor, sliding friction opposes its movement.
- Sliding down a playground slide: Friction acts between your clothes and the slide as you move downward.
Why the other options are incorrect:
- A. Static friction: Acts when surfaces are in contact but do not slide relative to each other.
- B. Rolling friction: Acts when an object rolls over a surface, such as a wheel rolling on a road.
- D. Fluid friction: Acts when an object moves through a fluid, such as air or water.
4. Which type of friction is generally the least?
Correct Answer: D. Rolling friction
Explanation: Rolling friction is the resistance experienced when an object rolls over a surface. In the usual school-level comparison, rolling friction is generally less than sliding friction. When an object rolls, it usually experiences less resistance than when it slides across a surface. This is why wheels and ball bearings are used to make movement easier and reduce friction in machines. The amount of friction depends on the materials and conditions involved.
Real-Life Examples:
- Wheeled suitcases: A suitcase with wheels is easier to pull than one dragged across the floor.
- Bicycles: Wheels help bicycles move with less resistance than sliding.
- Ball bearings: These allow machine parts to roll against each other, reducing friction.
Why the other options are incorrect:
- A. Static friction: Static friction prevents two surfaces from starting to slide relative to each other. Its maximum value is generally greater than rolling friction.
- B. Sliding friction: Sliding friction acts when one surface slides over another. It is generally greater than rolling friction.
- C. Fluid friction: Fluid friction acts when an object moves through a liquid or gas. Its magnitude depends on the object’s speed, shape and the fluid’s properties.
5. Friction mainly depends on:
Correct Answer: A. The material and roughness of the surfaces in contact
Explanation: Friction depends mainly on the nature of the materials and the condition of the surfaces in contact. Rough surfaces generally produce more friction because their tiny irregularities interact and resist movement. Smoother surfaces often produce less friction, although the actual friction also depends on how strongly the surfaces are pressed together. Understanding these factors helps us know when friction should be increased for safety and when it should be reduced to make movement easier.
Real-Life Examples:
- Shoe soles: Rough patterns on shoe soles provide better grip and help prevent slipping.
- Car tyres: Tread patterns help tyres maintain grip on the road.
- Ice skating: The slippery ice surface allows skates to move with relatively little resistance.
Why the other options are incorrect:
- B. The colour of the surfaces: Colour does not normally determine the friction between two surfaces.
- C. The shape of the object only: Shape alone does not determine friction between solid surfaces. The nature of the surfaces and the force pressing them together are also important.
- D. The volume of the object only: Volume alone does not determine friction. Other factors, such as the surfaces in contact and the force pressing them together, affect friction.
6. Which of the following increases friction?
Correct Answer: C. Making the surfaces rough
Explanation: Making surfaces rough generally increases friction because rough surfaces have tiny irregularities that interact with one another. When one surface moves or tries to move over another, these irregularities resist the movement. Increasing friction is useful when we need better grip, such as when walking, holding objects or stopping vehicles. In contrast, lubricants, polishing and ball bearings are commonly used to reduce friction in suitable situations.
Real-Life Examples:
- Shoe soles: Rough patterns improve grip and help us walk without slipping.
- Tyres: Tread patterns help vehicles maintain grip on roads.
- Sports equipment: Textured handles on bats and rackets help players hold them firmly.
Why the other options are incorrect:
- A. Applying lubricating oil: Oil forms a lubricating layer between surfaces and generally reduces friction.
- B. Polishing the surfaces: Polishing makes surfaces smoother and often reduces friction in the usual school-level context.
- D. Using ball bearings: Ball bearings replace much of the sliding contact with rolling contact, reducing friction in machines.
7. Which substance is commonly used to reduce friction in machines?
Correct Answer: A. Grease or lubricating oil
Explanation: Grease and lubricating oil are commonly used to reduce friction between moving parts of machines. They form a thin layer between the surfaces, reducing direct contact and helping the parts move smoothly. Lubricants also reduce wear and tear, prevent overheating, and help machines work efficiently. Without proper lubrication, moving parts may experience greater friction, produce more heat, and wear out faster.
Real-Life Examples:
- Bicycle chains: Lubricating oil helps the chain move smoothly and reduces wear.
- Car engines: Engine oil lubricates moving parts and reduces friction.
- Door hinges: Applying oil helps a squeaky hinge move more smoothly.
Why the other options are incorrect:
- B. Sand: Sand particles create rough contact between surfaces and generally increase friction.
- C. Rubber powder: Rubber powder is not commonly used as a lubricant in machines and may increase resistance between surfaces.
- D. Chalk powder: Chalk powder is not a standard lubricant for machine parts and does not provide the same protective lubricating layer as oil or grease.
8. Ball bearings are used mainly to:
Correct Answer: D. Reduce friction by converting sliding friction into rolling friction
Explanation: Ball bearings are mechanical components containing small, hard balls placed between moving parts. They reduce friction by allowing the parts to roll over the balls instead of sliding directly against each other. Rolling friction is generally less than sliding friction, so ball bearings help machinery move more smoothly. They also reduce wear and help improve the efficiency and lifespan of machines.
Real-Life Examples:
- Bicycle wheels: Ball bearings help the wheels rotate smoothly around their axles.
- Electric motors: Ball bearings support rotating shafts and reduce friction.
- Skateboards: Bearings inside the wheels allow them to rotate smoothly.
Why the other options are incorrect:
- A. Increase friction: Ball bearings are designed mainly to reduce friction, not increase it.
- B. Increase the weight of machines: Their main purpose is to reduce friction and support moving parts, not to increase machine weight.
- C. Convert rolling friction into sliding friction: Ball bearings do the opposite in the usual school-level explanation; they replace much of the sliding contact with rolling contact to reduce friction.
9. Which type of friction acts between a moving vehicle and air?
Correct Answer: C. Fluid friction
Explanation: Fluid friction is the resistance experienced by an object when it moves through a fluid. Fluids include liquids and gases, so air also produces fluid friction. When a vehicle moves, it pushes air aside, and the air exerts a resistive force called air resistance or drag. This force acts opposite to the vehicle’s motion. Air resistance generally increases as the vehicle’s speed increases and also depends on its shape and the surrounding air conditions.
Real-Life Examples:
- Moving car: Air resistance opposes a car as it travels along a road.
- Cycling: A cyclist feels greater air resistance when cycling at higher speeds.
- Parachute: Air resistance slows a person descending with an open parachute.
Why the other options are incorrect:
- A. Rolling friction: This occurs when an object rolls over a surface, such as a vehicle’s tyres rolling on a road.
- B. Sliding friction: This occurs when one solid surface slides over another, such as a box sliding across a floor.
- D. Static friction: This acts between surfaces that are in contact without sliding relative to each other, such as a stationary object that does not slip when a force is applied.
10. Which friction acts between the tyres of a vehicle and the road during normal rolling motion?
Correct Answer: A. Rolling friction
Explanation: Rolling friction is the resistance that occurs when an object rolls over a surface. During normal rolling motion, a vehicle’s tyres roll along the road, and rolling resistance opposes their motion. This resistance is generally smaller than the friction experienced when a tyre slides across the road. However, the contact between the tyres and the road also provides grip through static friction, which is essential for acceleration, braking and turning without slipping. For this question, the expected answer is rolling friction.
Real-Life Examples:
- Car tyres: Rolling resistance opposes the motion of tyres as a car travels along a road.
- Bicycle wheels: Rolling resistance acts as the wheels roll over the ground.
- Shopping trolley: Its wheels roll along the floor, experiencing rolling resistance.
Why the other options are incorrect:
- B. Sliding friction: This acts when one surface slides over another, such as when a locked tyre skids on the road.
- C. Fluid friction: This acts when an object moves through a fluid, such as air resistance acting on a moving vehicle.
- D. Static friction: Static friction provides grip between the tyre and the road when the tyre rolls without slipping. It is important in normal driving, but rolling friction is the expected answer for this question about resistance during rolling motion.
11. Walking is possible mainly because of:
Correct Answer: B. Friction between the feet and the ground
Explanation: Walking is possible mainly because of friction between our feet and the ground. When we walk, our foot pushes backward against the ground. Static friction from the ground acts forward on the foot, helping our body move forward without slipping. If there were insufficient friction, our feet would slide backward, making walking difficult. This is why walking on a dry, rough surface is generally easier than walking on a wet or slippery surface.
Real-Life Examples:
- Walking on a road: Friction between our shoes and the road helps us move forward.
- Running: Friction provides the grip needed to push against the ground.
- Walking on a wet floor: Reduced friction makes slipping more likely.
Why the other options are incorrect:
- A. Magnetic force: Walking does not normally depend on magnetic force because our feet and the ground are not using magnets to move us forward.
- C. Electrostatic force: Electrostatic force is not the main force responsible for ordinary walking.
- D. Gravitational force only: Gravity helps keep us on the ground, but gravity alone cannot provide the horizontal grip needed for walking. Friction is also essential.
12. Which of the following is an advantage of friction?
Correct Answer: C. It allows writing on paper.
Explanation: Friction is useful in many everyday activities. When we write with a pencil, friction between the pencil tip and the paper helps transfer graphite onto the paper, leaving visible marks. Friction also helps us walk without slipping, hold objects firmly and stop vehicles using brakes. Although friction can sometimes cause energy loss, heat and wear and tear, it is essential for many ordinary tasks.
Real-Life Examples:
- Writing: Friction between a pencil and paper allows us to write.
- Walking: Friction between our feet and the ground prevents slipping.
- Braking: Friction between brake pads and a disc or drum helps stop a vehicle.
- Holding objects: Friction helps us grip a glass or hold a book without it slipping from our hands.
Why the other options are incorrect:
- A. It causes wear and tear of machine parts: This is generally a disadvantage of friction because it gradually damages moving parts.
- B. It wastes energy as heat: This is a disadvantage because some useful mechanical energy is converted into heat.
- D. It increases fuel consumption: Excessive friction and resistance can increase the energy required to operate a vehicle, leading to greater fuel consumption.
13. Which of the following is a disadvantage of friction?
Correct Answer: D. It causes wear and tear of moving machine parts.
Explanation: Friction has both advantages and disadvantages. When two surfaces move against each other, friction can gradually wear away the materials in contact. This is called wear and tear. In machines, friction between moving parts can damage components over time, generate unwanted heat and reduce energy efficiency. Therefore, lubricants are often used to reduce friction and protect machine parts. However, friction is also necessary for activities such as walking, gripping objects and stopping vehicles.
Real-Life Examples:
- Machine parts: Continuous friction between moving parts can cause them to wear out over time.
- Vehicle tyres: Friction between tyres and the road gradually wears down the tyre surface.
- Shoe soles: Repeated contact with the ground causes shoe soles to wear away.
Why the other options are incorrect:
- A. It enables us to walk safely: This is an advantage because friction provides grip between our feet and the ground.
- B. It helps vehicles move: This is an advantage because friction between tyres and the road provides the grip needed for acceleration and movement.
- C. It increases grip between surfaces: This is an advantage because friction helps us hold objects firmly and prevents slipping.
14. Lubricants reduce friction by:
Correct Answer: B. Forming a thin layer between surfaces
Explanation: Lubricants such as oil and grease reduce friction by forming a thin layer between surfaces that move against each other. This layer reduces direct contact between the surfaces and allows them to move more smoothly. Lubrication also helps reduce wear and tear, prevents excessive heat generation and protects machine parts from damage. Proper lubrication is important for the smooth and efficient operation of engines and other machines.
Real-Life Examples:
- Car engines: Engine oil lubricates moving parts and reduces friction.
- Bicycle chains: Lubricating oil helps the chain move smoothly and reduces wear.
- Door hinges: Applying oil helps the hinge move smoothly and reduces squeaking.
Why the other options are incorrect:
- A. Increasing the roughness of surfaces: Increasing surface roughness generally increases friction rather than reducing it.
- C. Increasing the normal force: Increasing the force pressing two surfaces together generally increases the frictional force rather than reducing it.
- D. Increasing the weight of the machine: Increasing the machine’s weight does not reduce friction. If it increases the force pressing surfaces together, friction may increase.
15. Which type of friction acts on a body moving through water?
Correct Answer: C. Fluid friction
Explanation: Fluid friction is the resistance experienced by an object when it moves through a fluid. Fluids include liquids and gases, so water produces fluid friction when an object moves through it. This resistance acts opposite to the object’s motion. The amount of fluid friction depends on factors such as the object’s speed, shape and the properties of the fluid. As an object moves faster through water, the resistance generally increases.
Real-Life Examples:
- Swimming: Water resistance opposes a swimmer’s movement through water.
- Boats: Water resistance acts against a boat as it moves forward.
- Fish swimming: Fish experience water resistance as they move through water.
Why the other options are incorrect:
- A. Sliding friction: This acts when one solid surface slides over another, such as a book sliding across a table.
- B. Rolling friction: This acts when an object rolls over a surface, such as a wheel rolling along a road.
- D. Static friction: This acts between surfaces in contact when they do not slide relative to each other, such as a stationary box that does not slip when pushed gently.
16. Which statement about static friction is correct?
Correct Answer: B. It acts between surfaces before motion begins.
Explanation: Static friction acts between two surfaces in contact when they are not sliding relative to each other. It opposes the tendency of relative motion when an external force tries to move an object. Static friction adjusts according to the applied force, up to a maximum value. If the applied force exceeds this maximum value, the object begins to slide. Therefore, static friction helps keep objects at rest until the force applied is sufficient to overcome it.
Real-Life Examples:
- Pushing a cupboard: When you push a cupboard gently and it remains stationary, static friction prevents it from sliding.
- A book on a sloping surface: Static friction can prevent the book from sliding down the slope.
- Walking: Static friction between your feet and the ground provides grip and helps prevent slipping.
Why the other options are incorrect:
- A. It acts only on moving bodies: Incorrect because static friction acts when surfaces are not sliding relative to each other.
- C. It is always less than rolling friction: Incorrect because the maximum static friction is generally greater than rolling friction under comparable conditions.
- D. It is absent when a body is at rest: Incorrect because static friction can act on a stationary object when an external force tries to move it. However, if no horizontal force or tendency to slide exists, static friction may be zero.
17. Which method is used to increase friction in vehicle tyres?
Correct Answer: D. Providing treads on the tyres
Explanation: Treads are the grooves and patterns provided on vehicle tyres to improve grip on the road. They help tyres maintain contact with the road surface and channel water away from the contact area during wet conditions, reducing the risk of slipping due to loss of grip. Tyre tread design is especially important for safe braking, acceleration and turning. Worn-out tyres have reduced tread depth and may provide poorer grip, particularly on wet roads.
Real-Life Examples:
- Car tyres: Tread patterns help tyres maintain grip while driving and braking.
- Motorcycle tyres: Treads help provide traction on different road surfaces.
- Bicycle tyres: Suitable tread patterns help improve grip on roads and rough paths.
Why the other options are incorrect:
- A. Polishing the tyres: Polishing is not a method used to improve tyre grip and may make the surface unsuitable for traction.
- B. Applying grease on the tyres: Grease can make the tyre surface slippery and reduce grip, creating a safety hazard.
- C. Using smooth metal tyres: Smooth metal tyres generally do not provide the suitable road grip required for ordinary vehicles and can be dangerous on many road surfaces.
18. Which of the following has the least friction under ordinary conditions?
Correct Answer: C. Rolling friction
Explanation: Rolling friction is the resistance experienced when an object rolls over a surface. Under ordinary school-level conditions, rolling friction is generally less than sliding friction because a rolling object experiences less resistance than an object sliding across the same surface. This is why wheels and rollers make it easier to move heavy objects. The exact amount of friction depends on the materials and the conditions of contact.
Real-Life Examples:
- Wheeled suitcases: A suitcase with wheels is easier to move than one dragged across the floor.
- Bicycles: Wheels help a bicycle move with less resistance than sliding.
- Trolleys: Wheels make it easier to transport heavy goods across a floor.
Why the other options are incorrect:
- A. Static friction: Static friction prevents surfaces from starting to slide relative to each other. Its maximum value is generally greater than rolling friction.
- B. Sliding friction: Sliding friction acts when one surface slides over another and is generally greater than rolling friction.
- D. Fluid friction: Fluid friction acts when an object moves through a liquid or gas. Its magnitude depends on the object’s speed, shape and the properties of the fluid, so it cannot always be directly compared with the other types.
19. Which device helps reduce friction between rotating machine parts?
Correct Answer: A. Ball bearings
Explanation: Ball bearings are mechanical devices containing small, hard balls placed between moving parts. They reduce friction by allowing the parts to roll over the balls instead of sliding directly against each other. Since rolling friction is generally less than sliding friction, ball bearings help machine parts rotate smoothly. They also reduce wear and tear, limit energy loss and help improve the efficiency of machines.
Real-Life Examples:
- Bicycle wheels: Ball bearings help the wheels rotate smoothly around their axles.
- Electric motors: Ball bearings support rotating shafts and reduce resistance.
- Skateboards: Bearings inside the wheels help them rotate smoothly.
Why the other options are incorrect:
- B. Sandpaper: Sandpaper has a rough surface and is mainly used for smoothing materials by abrasion, not for reducing friction between rotating machine parts.
- C. Brake pads: Brake pads create friction against a disc or drum to slow down or stop a vehicle.
- D. Rubber blocks: Rubber blocks are not commonly used as bearings for rotating machine parts and may create considerable friction when rubbed against other surfaces.
20. Which statement is scientifically correct regarding friction?
Correct Answer: A. Friction can be both useful and harmful.
Explanation: Friction can be both useful and harmful, depending on the situation. It is useful because it allows us to walk without slipping, write on paper, grip objects and stop vehicles using brakes. Without sufficient friction, many everyday activities would become difficult or impossible. However, friction can also cause wear and tear of machine parts, generate unwanted heat and waste energy. Therefore, friction is increased when better grip is needed and reduced when smooth movement of machine parts is required.
Real-Life Examples:
- Walking: Friction between our feet and the ground helps us walk safely.
- Writing: Friction between a pencil and paper allows us to write.
- Vehicle brakes: Friction helps slow down and stop vehicles.
- Machines: Friction between moving parts can cause wear and tear and generate heat.
Why the other options are incorrect:
- B. Friction acts only between solids: Incorrect because friction also occurs in fluids, including liquids and gases. For example, air resistance acts on a moving vehicle.
- C. Friction always increases the speed of a body: Incorrect because friction often opposes motion or the tendency of relative motion. For example, friction between brake pads and a disc slows down a vehicle.
- D. Friction has no practical applications: Incorrect because friction is essential for walking, writing, gripping objects and operating brakes.
Quick Revision: Friction
Table 1: Types of Friction
| Type of Friction | Meaning | Example |
|---|---|---|
| Static friction | Prevents the start of sliding between surfaces at rest relative to each other | Pushing a cupboard that does not move |
| Sliding friction | Acts when one surface slides over another | A box sliding across the floor |
| Rolling friction | Resistance when an object rolls over a surface | A bicycle wheel rolling on a road |
| Fluid friction | Resistance experienced by an object moving through a liquid or gas | A swimmer moving through water |
Table 2: Important Facts About Friction
| Topic | Key Point |
|---|---|
| Direction of friction | Opposes relative motion or the tendency of relative motion |
| Factors affecting friction | Nature of the surfaces and the force pressing them together |
| Rolling friction | Generally less than sliding friction |
| Lubricants | Oil and grease reduce friction by forming a layer between surfaces |
| Ball bearings | Reduce friction by replacing much of the sliding contact with rolling contact |
| Rough surfaces | Generally provide greater grip |
| Tyre treads | Help tyres maintain grip on the road |
| Air resistance | A type of fluid friction |
| Water resistance | A type of fluid friction |
| Static friction | Can act even when an object remains stationary |
Table 3: Advantages and Disadvantages of Friction
| Advantages | Disadvantages |
|---|---|
| Helps us walk without slipping | Causes wear and tear |
| Allows us to write on paper | Produces unwanted heat |
| Helps vehicles stop using brakes | Wastes useful energy |
| Helps us grip and hold objects | Can increase energy consumption in machines |
| Provides grip between tyres and roads | Can damage moving machine parts |
Table 4: Methods of Increasing and Reducing Friction
| Method | Effect | Example |
|---|---|---|
| Making surfaces rough | Generally increases friction | Rough shoe soles |
| Providing tyre treads | Improves grip | Car tyres |
| Applying lubricating oil | Reduces friction | Car engines |
| Applying grease | Reduces friction | Machine components |
| Using ball bearings | Reduces friction | Bicycle wheels and electric motors |
| Using wheels or rollers | Makes moving objects easier | Wheeled suitcases |
Further Reference For Topic “Friction”
Further Reading: For a deeper understanding of friction, refer to the official NCERT Science textbook chapter on Friction. It explains the factors affecting friction, its advantages and disadvantages, methods of reducing friction through lubrication, rolling friction, and real-life applications. This additional resource will help you strengthen your Physics concepts and prepare for TNPSC General Science questions.
