TNPSC Physics Force Test 2 – Balanced and Unbalanced Forces

Test your understanding of Force with this TNPSC Physics Force Test covering balanced force, unbalanced force, resultant force, and equilibrium.
This quiz includes important MCQs to help you revise these Physics concepts and strengthen your TNPSC General Science preparation. This Physics Force Test contains carefully selected MCQs to help you check your understanding and revise these concepts before moving on to more advanced force and motion topics.

Note: Detailed explanations for every question are provided below the test to help you review the answers and strengthen your TNPSC exam preparation.

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Physics Force Test 2 : Balanced and Unbalanced Forces – Topic Highlights & Quick Revision

This section covers the key concepts of Force, including balanced and unbalanced forces, resultant force, and equilibrium. Understanding these concepts helps explain how forces acting on an object can either maintain its state of motion or cause a change in motion. These are important Physics concepts for TNPSC General Science preparation.

Topics covered:

• Balanced Force
• Unbalanced Force
• Resultant Force
• Equilibrium
• Effect of force on motion

1. Balanced forces acting on an object produce:

Correct Answer: Zero resultant force

Explanation:

• Balanced forces are equal in magnitude and opposite in direction.
• They cancel each other, so the resultant force is zero.
• Therefore, balanced forces do not produce acceleration due to a net force.
• The object can remain at rest or continue moving with constant velocity.

Additional Related Points: Balanced forces occur when the total force acting on an object is zero, which is known as equilibrium. An object in equilibrium can either be at rest or move with constant velocity. In contrast, unbalanced forces produce a non-zero resultant force and can change the motion of an object.

Real-Life Example: A book resting on a table experiences a downward gravitational force and an equal upward force from the table. These forces are balanced, so the resultant force is zero and the book remains at rest.

2. Which of the following is an example of balanced forces?

Correct Answer: A book resting on a table

Explanation:

• A book resting on a table is acted upon by two forces: the gravitational force acting downward and the normal force from the table acting upward.
• These forces are equal in magnitude and opposite in direction.
• Therefore, the resultant force is zero, and the book remains at rest.
• Hence, the forces acting on the book are balanced forces.

Additional Related Points: Balanced forces do not change the state of motion of an object. An object at rest remains at rest, while an object already moving can continue with constant velocity when the resultant force is zero. Balanced forces are therefore associated with equilibrium.

Real-Life Example: A wall clock hanging on a wall remains at rest because the downward gravitational force is balanced by the upward supporting force provided by the wall or its support.

3. Unbalanced forces acting on a body can change its:

Correct Answer: State of motion

Explanation:

• Unbalanced forces occur when the forces acting on a body are not equal and opposite.
• They produce a non-zero resultant force.
• This resultant force can change the state of motion of the body.
• It can make an object start moving, stop, speed up, slow down, or change its direction.

Additional Related Points: According to Newton’s laws of motion, a non-zero resultant force produces acceleration. The acceleration may involve a change in the speed or direction of motion. Unlike balanced forces, unbalanced forces do not keep an object in equilibrium.

Real-Life Example: When a football is kicked, the force applied by the foot is unbalanced and changes the ball’s state of motion. The ball moves from rest and may also change its direction when kicked from different angles.

4. The net force acting on a body is called the:

Correct Answer: Resultant force

Explanation:

• The net force is the overall force acting on a body after considering all the forces acting on it.
• This overall force is called the resultant force.
• It determines whether the forces are balanced or unbalanced.
• If the resultant force is zero, the forces are balanced; if it is non-zero, the forces are unbalanced.

Additional Related Points: Resultant force is found by considering both the magnitude and direction of the forces acting on an object. When forces act in the same direction, their effects add together, while forces acting in opposite directions are compared to find the net effect.

Real-Life Example: When two people push a box in the same direction, their pushes combine to produce a greater resultant force, making it easier to move the box.

5. When two equal and opposite forces act on a body, the resultant force is:

Correct Answer: Zero

Explanation:

• Two forces are equal and opposite when they have the same magnitude but act in opposite directions.
• Their effects cancel each other.
• Therefore, the resultant force is zero.
• Such forces are called balanced forces.

Additional Related Points: When the resultant force is zero, the object is in equilibrium. An object at rest remains at rest, while an object already moving continues with constant velocity, provided no other unbalanced force acts on it.

Real-Life Example: A book resting on a table experiences gravity pulling it downward and an equal upward normal force from the table. The two forces are opposite and equal, so the resultant force on the book is zero.

6. A body remains in equilibrium when:

Correct Answer: The resultant force is zero

Explanation:

• A body is in equilibrium when the forces acting on it are balanced.
• This means the resultant force acting on the body is zero.
• When the resultant force is zero, the body has no acceleration due to a net force.
• The body can either remain at rest or continue moving with constant velocity.

Additional Related Points: Equilibrium does not always mean that an object is stationary. A moving object can also be in equilibrium if it moves with constant velocity. In both cases, the resultant force is zero and there is no change in its state of motion.

Real-Life Example: A book kept on a table is in equilibrium because the downward gravitational force is balanced by the upward normal force exerted by the table. The resultant force on the book is zero.

7. Which of the following can produce acceleration?

Correct Answer: Unbalanced forces

Explanation:

• Unbalanced forces produce a non-zero resultant force on an object.
• According to Newton’s Second Law of Motion, a net force produces acceleration.
• Acceleration can change the speed, direction, or both of an object’s motion.
• Therefore, unbalanced forces can produce acceleration.

Additional Related Points: Balanced forces have a zero resultant force and therefore do not produce acceleration. When an unbalanced force acts on a body, the resulting acceleration occurs in the direction of the net force. The greater the net force for a given mass, the greater the acceleration.

Real-Life Example: When a football is kicked, the force applied by the foot is unbalanced. This produces acceleration and changes the ball from a state of rest to motion.

8. A force of 15 N acts eastward and a force of 5 N acts westward on the same body. The resultant force is:

Correct Answer: 10 N eastward

Explanation:

• The two forces act in opposite directions, so their magnitudes are subtracted.
• Resultant force = 15 N − 5 N = 10 N.
• The larger force is 15 N acting eastward.
• Therefore, the resultant force is 10 N eastward.
• Since the resultant force is not zero, the forces are unbalanced.

Additional Related Points: When forces act in opposite directions, the resultant force acts in the direction of the larger force. If two opposite forces have equal magnitude, the resultant force becomes zero and the forces are balanced. The resultant force determines the direction of acceleration of a body.

Real-Life Example: If two people push a box in opposite directions, with one person applying a force of 15 N eastward and the other 5 N westward, the box experiences a resultant force of 10 N eastward.

9. Which condition is necessary for balanced forces?

Correct Answer: The forces must act in opposite directions with equal magnitude.

Explanation:

• Balanced forces must have equal magnitudes and act in opposite directions.
• Their effects cancel each other, making the resultant force zero.
• Balanced forces do not produce acceleration or change the state of motion.
• The body may be at rest or moving with constant velocity.

Additional Related Points: Balanced forces can act on an object even when it is moving. The important condition is that the total or resultant force must be zero. Forces acting in the same direction add together and therefore cannot balance each other unless other opposing forces are also present.

Real-Life Example: When a book rests on a table, the gravitational force acting downward is balanced by the normal force acting upward. The two forces are equal and opposite, so the resultant force is zero.

10. If the resultant force acting on a body is zero, the body:

Correct Answer: May remain at rest or move with constant velocity

Explanation:

• A zero resultant force means that all the forces acting on the body are balanced.
• According to Newton’s First Law of Motion, there is no acceleration when the resultant force is zero.
• If the body is at rest, it remains at rest.
• If the body is already moving, it continues with constant velocity.

Additional Related Points: A zero resultant force does not mean that no forces are acting on the body. Several forces may act on an object and still produce a zero net force when they balance each other. This condition is known as equilibrium.

Real-Life Example: A passenger sitting inside a bus moving at constant speed in a straight line can continue moving with the bus because there is no net force causing acceleration. If the bus is stationary, the passenger remains at rest.

11. Which of the following is an example of unbalanced forces?

Correct Answer: A cyclist applying brakes and slowing down

Explanation:

• When a cyclist applies the brakes, a frictional force acts against the direction of motion.
• This produces an unbalanced force on the bicycle.
• The resultant force causes the bicycle to decelerate, meaning its speed decreases.
• Therefore, the cyclist slows down because of an unbalanced force.

Additional Related Points: An unbalanced force can change the speed or direction of a moving object. It produces a non-zero resultant force and therefore causes acceleration. Acceleration can be positive or negative depending on whether the object’s speed increases or decreases.

Real-Life Example: When a cyclist presses the brake lever, the brake pads create friction against the wheel. This opposing force reduces the bicycle’s speed and eventually brings it to rest.

12. A force of 12 N acts northward and another force of 12 N acts southward on a body. The resultant force is:

Correct Answer: Zero

Explanation:

• The two forces have the same magnitude (12 N).
• They act in opposite directions, one northward and the other southward.
• Therefore, their effects cancel each other.
• The resultant force is zero, so the forces are balanced.

Additional Related Points: When two equal and opposite forces act on a body, the net or resultant force is zero. Such a body is in equilibrium and has no acceleration due to the net force. Equal forces in opposite directions are a common example of balanced forces.

Real-Life Example: A book resting on a table has the downward force of gravity balanced by the upward normal force from the table. The two forces cancel, giving a resultant force of zero.

13. The SI unit of resultant force is:

Correct Answer: Newton

Explanation:

• Resultant force is the net effect of all forces acting on a body.
• Since resultant force is a type of force, its SI unit is the newton (N).
• The newton is named after Sir Isaac Newton, who formulated the laws of motion.
• One newton is the force required to give a mass of 1 kg an acceleration of 1 m/s².

Additional Related Points: Force is measured in newtons (N) in the SI system. Other physical quantities have different SI units: energy is measured in joules, power in watts, and pressure in pascals. Remembering these units is useful for TNPSC Physics questions.

Real-Life Example: If you push a box with a force of 10 N, the force acting on the box is measured in newtons. If another force acts in the opposite direction, the resultant force is calculated by considering both forces.

14. Which quantity determines the combined effect of all forces acting on a body?

Correct Answer: Resultant force

Explanation:

• The resultant force is the combined effect of all forces acting on a body.
• It is also called the net force.
• It is found by considering the magnitude and direction of all the forces.
• A zero resultant force means the forces are balanced, while a non-zero resultant force means they are unbalanced.

Additional Related Points: The resultant force determines whether the motion of a body will change. If the resultant force is zero, there is no acceleration due to the net force. If it is non-zero, the body can accelerate.

Real-Life Example: When two people push a box in the same direction, their forces combine to produce a larger resultant force, making the box move more easily.

15. Which statement about balanced forces is correct?

Correct Answer: They do not change the state of motion of a body.

Explanation:

• Balanced forces have a resultant force of zero.
• Therefore, they do not produce acceleration.
• An object at rest remains at rest.
• An object already moving continues with constant velocity.

Additional Related Points: Balanced forces do not mean that no forces are acting on an object. Forces can act on an object and still balance each other when their total resultant is zero. This condition is called equilibrium.

Real-Life Example: A book resting on a table remains at rest because the downward gravitational force is balanced by the upward normal force from the table.

16. A force of 30 N acts eastward and another force of 10 N acts eastward on the same body. The resultant force is:

Correct Answer: 40 N eastward

Explanation:

• Both forces act in the same direction.
• Therefore, their magnitudes are added.
• Resultant force = 30 N + 10 N = 40 N.
• The resultant force acts eastward, in the same direction as the two forces.
• Since the resultant force is non-zero, the forces are unbalanced.

Additional Related Points: When forces act in the same direction, their effects add together. When forces act in opposite directions, the smaller force is subtracted from the larger force to find the resultant force.

Real-Life Example: If two people push a box eastward with forces of 30 N and 10 N, the box experiences a resultant force of 40 N eastward.

17. Which of the following situations represents equilibrium?

Correct Answer: A book resting on a table

Explanation:

• A book resting on a table experiences a downward gravitational force.
• The table exerts an upward normal force on the book.
• These forces are equal and opposite, so the resultant force is zero.
• Therefore, the book is in equilibrium.

Additional Related Points: In basic force problems, an object is in translational equilibrium when the resultant force acting on it is zero. An object in equilibrium can be at rest or move with constant velocity.

Real-Life Example: A book kept on a table remains stationary because the downward gravitational force is balanced by the upward normal force from the table.

18. Unbalanced forces can change the:

Correct Answer: Speed and direction of a body

Explanation:

• Unbalanced forces produce a non-zero resultant force.
• They can change the speed of a moving body.
• They can also change the direction of its motion.
• Therefore, an unbalanced force can change both the speed and direction of a body.

Additional Related Points: According to Newton’s Second Law of Motion, a non-zero resultant force produces acceleration. Acceleration means a change in velocity, which can involve a change in speed, direction, or both.

Real-Life Example: When a football is kicked at an angle, the force can change both its speed and direction of motion.

19. A force of 25 N acts rightward and a force of 15 N acts leftward on a body. The resultant force is:

Correct Answer: 10 N rightward

Explanation:

• The two forces act in opposite directions, so their magnitudes are subtracted.
• Resultant force = 25 N − 15 N = 10 N.
• The larger force is 25 N and acts rightward.
• Therefore, the resultant force is 10 N rightward.
• Since the resultant force is not zero, the forces are unbalanced.

Additional Related Points: When two forces act in opposite directions, the resultant force acts in the direction of the larger force. If the two forces were equal, the resultant force would be zero and the forces would be balanced.

Real-Life Example: If two people pull a box in opposite directions with forces of 25 N and 15 N, the box experiences a resultant force of 10 N toward the person applying 25 N.

20. Which statement is scientifically correct?

Correct Answer: Resultant force is the vector sum of all forces acting on a body.

Explanation:

• The resultant force is the overall or net force acting on a body.
• It is obtained by considering the magnitude and direction of all the forces.
• Therefore, it is the vector sum of all forces acting on the body.
• A zero resultant force indicates balanced forces, while a non-zero resultant force indicates unbalanced forces.

Additional Related Points: Resultant force determines the net effect of all forces on a body. When the resultant force is zero, an object can remain at rest or continue moving with constant velocity. When the resultant force is non-zero, the body can accelerate.

Real-Life Example: If two people push a box eastward with 20 N and 10 N, the resultant force is 30 N eastward. If another 30 N force acts westward, the resultant force becomes zero.

Further Reference For TNPSC Force – Balanced and Unbalanced Force

This Physics Force Test for TNPSC preparation covers important concepts such as balanced force, unbalanced force, resultant force, and equilibrium. For a deeper understanding of how multiple forces affect the motion of an object, students can refer to the NCERT Science chapter How Forces Affect Motion. NCERT also explains the conditions for mechanical and translational equilibrium in its Physics text. These references can help students strengthen their understanding of Physics concepts before attempting further TNPSC questions

NCERT Reference:

• NCERT Grade 9 Science – How Forces Affect Motion
• NCERT Physics – Systems of Particles and Rotational Motion