Test your preparation with TNPSC Physics Motion Test 4 questions designed for General Science revision. This Physics Motion Test focuses on important concepts related to motion and helps you check how well you can apply them in exam-style questions. Attempt all the questions and use the explanations to strengthen your understanding before the TNPSC examination.
Note: Detailed explanation for each question given below the Test, which will helping you understand the concept clearly and avoid common mistakes.
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TNPSC Physics Motion Test 4 – All Questions Detailed Explanation
Each question in this TNPSC Physics Motion Test is explained with a clear reason for the correct answer. The explanations highlight the important principles of acceleration, velocity, retardation, and related motion concepts, helping you understand the reasoning behind each answer and improve your accuracy in TNPSC Physics Questions.
1. Acceleration is defined as the
Answer: C. Rate of change of velocity
Explanation:
Acceleration is the rate at which the velocity of an object changes with time. Velocity can change when the speed of an object increases or decreases, or when its direction of motion changes. Therefore, an object can have acceleration even when its speed remains constant if its direction changes. The SI unit of acceleration is metre per second squared (m/s²).
Real-Life Example:
When a car starts from rest and gradually increases its speed, its velocity changes with time. Therefore, the car is said to be accelerating.
2. The SI unit of acceleration is
Answer: C. m/s²
Explanation:
Acceleration is the rate of change of velocity with time. The SI unit of velocity is metre per second (m/s). When the change in velocity is divided by time measured in seconds, the resulting unit is metre per second per second, written as m/s². It tells us how much the velocity changes in each second.
Real-Life Example:
If a car has an acceleration of 5 m/s², its velocity increases by 5 m/s every second, provided the acceleration remains constant.
3. An object is said to have uniform acceleration if it
Answer: B. Changes velocity by equal amounts in equal intervals of time
Explanation:
Uniform acceleration means that the velocity of an object changes by equal amounts in equal intervals of time. The change in velocity may be an increase or decrease, but the rate of change remains constant. For example, if the velocity increases by 5 m/s every second, the acceleration remains constant at 5 m/s². Covering equal distances in equal intervals of time indicates uniform speed, not necessarily uniform acceleration.
Real-Life Example:
An object falling freely near the Earth’s surface, when air resistance is neglected, undergoes approximately uniform acceleration due to gravity.
4. Which of the following is a vector quantity?
Answer: D. Acceleration
Explanation:
A vector quantity has both magnitude and direction. Acceleration is a vector quantity because it describes the rate of change of velocity, and velocity itself has both magnitude and direction. Therefore, the direction of acceleration is important when describing the motion of an object. In contrast, speed, distance, and time are scalar quantities, which have magnitude only.
Real-Life Example:
When a car moves around a curved road at constant speed, its direction keeps changing. Since its velocity changes due to the change in direction, the car has acceleration.
5. Positive acceleration means that the velocity of an object
Answer: C. Increases with time
Explanation:
Positive acceleration generally means that the velocity of an object is increasing in the chosen positive direction. When the velocity changes by a positive amount over time, the acceleration is positive. For motion along a straight line, this usually means the object is speeding up in the positive direction. However, the sign of acceleration depends on the direction chosen as positive, so positive acceleration does not always simply mean an increase in speed.
Real-Life Example:
A car moving forward increases its velocity from 10 m/s to 20 m/s in a few seconds. If the forward direction is taken as positive, the car has positive acceleration.
6. Negative acceleration is also called
Answer: B. Retardation
Explanation:
When acceleration acts opposite to the direction of motion and causes the velocity of an object to decrease, it is commonly called retardation or deceleration. It represents a reduction in the velocity of the object with time. For example, when a moving car is brought to a stop by applying brakes, its velocity decreases and the car undergoes retardation.
Real-Life Example:
When a driver applies the brakes to a moving car, the car gradually slows down. The decrease in velocity is due to retardation.
7. A body moving with constant velocity has
Answer: C. Zero acceleration
Explanation:
Acceleration is the rate of change of velocity with time. When a body moves with constant velocity, its velocity does not change in either magnitude or direction. Therefore, there is no change in velocity, and the acceleration of the body is zero.
Real-Life Example:
A car moving in a straight line at a constant velocity of 20 m/s has zero acceleration, as long as its speed and direction remain unchanged.
8. Which quantity changes during acceleration?
Answer: B. Velocity
Explanation:
Acceleration occurs when the velocity of an object changes with time. The change may be in the magnitude of velocity, its direction, or both. Therefore, velocity is the quantity directly associated with acceleration. Mass, density, and volume do not necessarily change when an object accelerates.
Real-Life Example:
When a moving bicycle speeds up, its velocity increases with time. This change in velocity means that the bicycle is accelerating.
9. Acceleration can occur due to a change in
Answer: C. Both speed and direction
Explanation:
Acceleration is the rate of change of velocity with time. Since velocity depends on both speed and direction, acceleration can occur when the speed changes, when the direction changes, or when both change. Therefore, an object moving at constant speed can still be accelerating if its direction continuously changes.
Real-Life Example:
A car moving around a circular track at constant speed is accelerating because its direction of motion changes continuously.
10. Which of the following motions has zero acceleration?
Answer: A. Uniform motion in a straight line with constant velocity
Explanation:
A body has zero acceleration when its velocity remains constant. In straight-line motion, if the object continues to move with the same speed in the same direction, there is no change in velocity. Since acceleration is the rate of change of velocity, its value is zero. Constant-speed circular motion, however, has acceleration because the direction of velocity changes continuously.
Real-Life Example:
A train moving in a straight line at a constant velocity has zero acceleration as long as its speed and direction remain unchanged.
11. A freely falling body near the Earth’s surface experiences
Answer: B. Constant acceleration due to gravity
Explanation:
A freely falling body is an object that moves under the influence of gravity alone, when effects such as air resistance are neglected. Near the Earth’s surface, the acceleration produced by gravity remains approximately constant and is directed towards the centre of the Earth. This acceleration is called acceleration due to gravity and is represented by g.
Real-Life Example:
When a stone is dropped from a height, it falls towards the ground because of Earth’s gravitational pull. Its velocity increases as it falls due to acceleration caused by gravity.
12. The acceleration due to gravity near the Earth’s surface is approximately
Answer: C. 9.8 m/s²
Explanation:
The acceleration produced by Earth’s gravitational force on a freely falling object near the Earth’s surface is approximately 9.8 m/s². This means that, when air resistance is neglected, the velocity of a freely falling object changes by about 9.8 m/s every second. The value is represented by the symbol g and is commonly taken as 9.8 m/s² in physics calculations.
Real-Life Example:
If an object is dropped from rest, its downward velocity increases by approximately 9.8 m/s during the first second, assuming air resistance is neglected.
13. When a vehicle slows down, it experiences
Answer: C. Retardation
Explanation:
When a vehicle slows down, its velocity decreases with time. Since acceleration is the rate of change of velocity, a decrease in velocity in the direction of motion is described as retardation or deceleration. Retardation indicates that the vehicle’s velocity is reducing over time.
Real-Life Example:
When a driver applies the brakes, the vehicle gradually slows down because its velocity decreases. This decrease in velocity is called retardation.
14. Which instrument is commonly used to measure time while determining acceleration?
Answer: A. Stopwatch
Explanation:
Acceleration is calculated from the change in velocity divided by the time taken. Therefore, accurate measurement of time is important when determining acceleration experimentally. A stopwatch is commonly used to measure the time interval between two events. The other instruments measure different physical quantities: an ammeter measures electric current, a speedometer measures speed, and a thermometer measures temperature.
Real-Life Example:
In a simple motion experiment, a stopwatch can be used to record how long an object takes to travel a measured distance. This time measurement can then be used along with velocity data to study its acceleration.
15. Which of the following is an example of accelerated motion?
Answer: B. A car increasing its speed on a straight road
Explanation:
Accelerated motion occurs when the velocity of an object changes with time. When a car increases its speed while moving in a straight line, its velocity increases, provided its direction remains unchanged. Therefore, the car experiences acceleration. An object at rest or an object moving with constant velocity has no acceleration.
Real-Life Example:
When a car moves from 20 m/s to 30 m/s on a straight road, its velocity increases with time. Hence, the car is undergoing accelerated motion.
16. If the velocity of an object decreases uniformly, its acceleration is
Answer: C. Negative
Explanation:
Acceleration is the rate of change of velocity with time. When the velocity of an object decreases uniformly, there is an equal decrease in velocity during equal intervals of time. Taking the direction of motion as positive, this change in velocity is negative, so the acceleration is negative. Such acceleration is commonly referred to as retardation.
Real-Life Example:
When a moving car is brought to a stop by applying its brakes, its velocity decreases with time. If the decrease is uniform, the car has uniform negative acceleration.
17. Acceleration is measured as
Answer: C. Change in velocity per unit time
Explanation:
Acceleration is defined as the change in velocity per unit time. It tells us how quickly the velocity of an object changes during a given time interval. Mathematically, acceleration is expressed as a = (v − u) / t, where u is the initial velocity, v is the final velocity, and t is the time taken. The SI unit of acceleration is m/s².
Real-Life Example:
If a car’s velocity changes from 10 m/s to 20 m/s in 5 seconds, its acceleration is (20 − 10) / 5 = 2 m/s².
18. A body moving in a circular path with constant speed has
Answer: B. Acceleration towards the centre of the circle
Explanation:
A body moving in a circular path has continuously changing direction of velocity, even when its speed remains constant. Since a change in velocity produces acceleration, the body experiences centripetal acceleration. This acceleration is always directed towards the centre of the circular path and keeps the body moving along the curved path. Therefore, uniform circular motion is an accelerated motion.
Real-Life Example:
A stone tied to a string and whirled in a circle experiences centripetal acceleration towards the centre of the circle. The string provides the inward force required to maintain the circular motion.
19. Which statement is correct regarding acceleration?
Answer: B. Acceleration can be positive, negative, or zero.
Explanation:
Acceleration is the rate of change of velocity with time. Its value depends on how the velocity changes relative to the chosen positive direction. Acceleration can be positive when velocity changes in the positive direction, negative when the change is in the opposite direction, or zero when velocity remains constant. Therefore, acceleration is not always positive. Since acceleration is a vector quantity, it has both magnitude and direction.
Real-Life Example:
A car speeding up in the forward direction may have positive acceleration, while a car slowing down may have negative acceleration. A car moving with constant velocity in a straight line has zero acceleration.
20. Which of the following best describes acceleration?
Answer: C. Change in velocity with respect to time
Explanation:
Acceleration is defined as the rate of change of velocity with respect to time. It occurs whenever the velocity of an object changes in magnitude, direction, or both. The mathematical expression for acceleration is a = (v − u) / t, where u is the initial velocity, v is the final velocity, and t is the time taken. The SI unit of acceleration is m/s².
Real-Life Example:
When a cyclist increases speed from 5 m/s to 10 m/s in 2 seconds, the change in velocity occurs over time, so the cyclist experiences acceleration.
Further Reference Material For TNPSC Motion
To understanding TNPSC Physics Motion, refer to the NCERT Class 9 Science chapter “Describing Motion Around Us.” This chapter covers distance and displacement, speed and velocity, scalar and vector quantities, SI units, and different types of motion, making it a useful reference for TNPSC Physics, General Science, and TNPSC exam preparation.
