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APPLICATION MASTERCLASS 06

REVERSAL OF MOTION

20-Second Physics Challenge
Trigger Recognition & Trap Elimination

REV-01

A ball is projected vertically upward. At the instant it reaches the highest point, its velocity changes from

Correct Answer: A

Trigger

Direction reversal

Formula / Tool

Velocity Sign Analysis

Quick Execution

Upward motion

v = 0

then

Downward motion
Trap: Treating the highest point as the end of motion.

REV-02

A particle moving in the positive x-direction has a velocity of +5 m/s. After some time, its velocity becomes −5 m/s. During this interval, the particle must have

Correct Answer: C

Trigger

Velocity sign reversal

Formula / Tool

Continuity of Motion

Quick Execution

+5

↓

0

↓

−5
Trap: Assuming velocity can change sign without becoming zero.

REV-03

A car moving at 20 m/s is uniformly retarded. The instant it comes to rest, the motion is

Correct Answer: B

Trigger

Stopping state

Formula / Tool

Boundary-State Recognition

Quick Execution

v = 0

Possible turning point

Future motion determines whether reversal occurs.
Trap: Assuming stopping automatically means reversal has already occurred.

REV-04

A ball thrown vertically upward is at its highest point. Which quantity changes direction immediately after this instant?

Correct Answer: C

Trigger

Highest-point reversal

Formula / Tool

State-Transition Recognition

Quick Execution

Velocity changes

Upward

↓

Downward
Trap: Assuming acceleration changes direction.

REV-05

A particle has velocity −10 m/s and acceleration +5 m/s². A reversal of motion is

Correct Answer: B

Trigger

Future reversal accessibility

Formula / Tool

Sign Analysis

Quick Execution

Velocity = Negative

Acceleration = Positive

Acceleration opposes motion

Speed decreases

Future reversal is possible.
Trap: Looking only at the present velocity.

REV-11

A particle moving at 20 m/s is retarded uniformly at 5 m/s². The time at which reversal becomes possible is

Correct Answer: B

Trigger

Reversal time

Formula / Tool

v = u + at

Quick Execution

0 = 20 − 5t

5t = 20

t = 4 s
Trap: Confusing reversal time with stopping distance.

REV-12

A particle starts with velocity 10 m/s and acceleration −2 m/s². Its velocity becomes zero after

Correct Answer: B

Trigger

Stopping time

Formula / Tool

v = u + at

Quick Execution

0 = 10 − 2t

2t = 10

t = 5 s
Trap: Using displacement equations instead of velocity equations.

REV-13

A particle moving right has positive velocity and negative acceleration. Its speed is

Correct Answer: B

Trigger

Velocity–acceleration sign logic

Formula / Tool

Sign Analysis

Quick Execution

Velocity → Positive

Acceleration → Negative

Acceleration opposes motion

Speed decreases
Trap: Looking only at the sign of acceleration.

REV-14

A particle moving left has negative velocity and negative acceleration. Its speed is

Correct Answer: A

Trigger

Velocity–acceleration sign logic

Formula / Tool

Sign Analysis

Quick Execution

Velocity → Negative

Acceleration → Negative

Same direction

Speed increases
Trap: Assuming negative acceleration always decreases speed.

REV-15

A particle moving right slows down continuously. At the turning point its velocity is

Correct Answer: C

Trigger

Turning-point state

Formula / Tool

Reversal Recognition

Quick Execution

Positive velocity

↓

v = 0

↓

Negative velocity
Trap: Choosing a small positive velocity instead of zero.

REV-16

A ball projected vertically upward reaches its highest point after 3 s. The reversal occurs after

Correct Answer: C

Trigger

Reversal time

Formula / Tool

Vertical Motion

Quick Execution

Direction changes at the highest point.

Highest point reached after 3 s.

Therefore reversal occurs at 3 s.
Trap: Assuming reversal occurs after the particle starts moving downward.

REV-17

A particle reverses its direction. Which quantity must change sign?

Correct Answer: B

Trigger

Direction reversal

Formula / Tool

Velocity Sign Analysis

Quick Execution

Reversal means motion changes direction.

Direction is carried by velocity.

Velocity must change sign.
Trap: Assuming position must also change sign.

REV-18

In a displacement–time graph, reversal occurs where the slope

Correct Answer: C

Trigger

Graph-based reversal

Formula / Tool

Slope = Velocity

Quick Execution

Positive slope

↓

Zero slope

↓

Negative slope

Direction reverses.
Trap: Looking for maximum displacement instead of velocity sign change.

REV-19

A particle moving right experiences a constant leftward acceleration. A future reversal is

Correct Answer: B

Trigger

Future reversal accessibility

Formula / Tool

Acceleration-Velocity Sign Logic

Quick Execution

Velocity → Right

Acceleration → Left

Speed decreases.

Reversal may occur after velocity reaches zero.
Trap: Ignoring the effect of acceleration on future motion.

REV-20

A particle reverses direction. At the reversal point, its displacement from the origin is necessarily

Correct Answer: D

Trigger

Reversal position

Formula / Tool

State Analysis

Quick Execution

Reversal only requires velocity = 0 at the turning point.

Position may be positive, negative, or zero.
Trap: Assuming every turning point occurs at the origin.

Continue Learning

Combine reversals, accessibility and multiple phases into complete motion stories.

Accessibility Questions

Can a state, position or event be reached?

Pursuit Problems

Catch-up situations and interception logic.

Multi-Stage Motion

Motion involving multiple phases and transitions.

Graph Intelligence

Use graphs to predict motion behaviour and turning points.