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APPLICATION MASTERCLASS 05

Accessibility Analysis

20-Second Physics Challenge
Trigger Recognition & Trap Elimination

AC-01

A particle is projected vertically upward with a speed of 20 m/s. Can it reach a point 25 m above the launch point?

Correct Answer: B

Trigger

Reachability

Formula / Tool

hmax = u²/2g

Quick Execution

hmax

= 20²/20

= 20 m

25 m is not reachable.
Trap: Checking time instead of maximum reachable height.

AC-02

A car moving at 20 m/s can retard at 5 m/s². A wall is 30 m ahead. Will the car stop before reaching the wall?

Correct Answer: B

Trigger

Stopping accessibility

Formula / Tool

v² = u² + 2as

Quick Execution

Stopping distance

= 20²/(2×5)

= 40 m

Wall is only 30 m away.
Trap: Calculating stopping time instead of stopping possibility.

AC-03

A particle starts from rest with an acceleration of 2 m/s². Can it cover 100 m in 5 s?

Correct Answer: B

Trigger

Distance accessibility

Formula / Tool

s = ½at²

Quick Execution

s

= ½(2)(5)²

= 25 m

100 m is not reachable.
Trap: Assuming acceleration guarantees reachability.

AC-04

A stone is thrown vertically upward with a speed of 30 m/s. Can it reach a height of 40 m?

Correct Answer: A

Trigger

Maximum-height accessibility

Formula / Tool

hmax = u²/2g

Quick Execution

hmax

= 30²/20

= 45 m

40 m is reachable.
Trap: Comparing speed directly with height.

AC-05

Two runners move in the same direction at 10 m/s and 8 m/s. The faster runner is 20 m behind. Can the faster runner eventually catch the slower runner?

Correct Answer: A

Trigger

Catch accessibility

Formula / Tool

Relative Velocity

Quick Execution

Relative speed

= 10 − 8

= 2 m/s

Relative speed > 0

Catch is possible.
Trap: Focusing only on the initial gap.

AC-06

Two runners move at equal speeds. One is 50 m behind the other. Can the trailing runner ever catch up?

Correct Answer: B

Trigger

Impossible accessibility

Formula / Tool

Relative Velocity

Quick Execution

Relative speed

= 0

No catch is possible.
Trap: Assuming enough time guarantees catching up.

AC-07

A particle moving at 15 m/s is uniformly retarded at 3 m/s². Can it travel 50 m before coming to rest?

Correct Answer: B

Trigger

Stopping accessibility

Formula / Tool

v² = u² + 2as

Quick Execution

Stopping distance

= 15²/(2×3)

= 37.5 m

50 m is not reachable.
Trap: Using time instead of stopping distance.

AC-08

A particle starts from rest with an acceleration of 4 m/s². Can it attain a speed of 50 m/s in 10 s?

Correct Answer: B

Trigger

Velocity accessibility

Formula / Tool

v = u + at

Quick Execution

v

= 0 + 4×10

= 40 m/s

50 m/s is not reachable.
Trap: Using the displacement equation.

AC-09

A ball is thrown vertically upward. Which point is definitely reachable?

Correct Answer: B

Trigger

Boundary state

Formula / Tool

Maximum Height Concept

Quick Execution

The highest point

is always reached

before reversal of motion.
Trap: Ignoring the boundary condition.

AC-10

A train moving with constant speed is 100 m from a station. If its speed remains unchanged, can it stop exactly at the station without braking?

Correct Answer: B

Trigger

Stopping event accessibility

Formula / Tool

State-Transition Recognition

Quick Execution

No deceleration

⇒ No stopping event

Position may be reached, but the stopped state cannot be reached.
Trap: Confusing position accessibility with state accessibility.

AC-11

A particle starts from rest and accelerates uniformly. Can its displacement remain zero after 5 s?

Correct Answer: B

Trigger

State accessibility

Formula / Tool

Uniformly Accelerated Motion

Quick Execution

s = ½at²

For positive acceleration and t > 0,

s > 0
Trap: Mixing displacement with velocity.

AC-12

A body is projected vertically upward with speed u. Which velocity is definitely accessible?

Correct Answer: B

Trigger

Velocity accessibility

Formula / Tool

Vertical Motion

Quick Execution

At launch,

velocity = u

The initial state is always accessible.
Trap: Ignoring the initial state.

AC-13

A car moving at 30 m/s can brake with a retardation of 10 m/s². A barrier is 40 m ahead. Will a collision occur?

Correct Answer: A

Trigger

Collision accessibility

Formula / Tool

Stopping Distance

Quick Execution

Stopping distance

= 30²/(2×10)

= 45 m

Barrier is only 40 m away.
Trap: Checking stopping time instead of stopping distance.

AC-14

A runner accelerates continuously. Is overtaking a constant-speed runner always impossible?

Correct Answer: B

Trigger

Future accessibility

Formula / Tool

Velocity Evolution

Quick Execution

Speed can continue increasing.

Eventually it may exceed the speed of the runner ahead.
Trap: Judging only from the initial state.

AC-15

A particle has zero velocity at an instant. Is motion after that instant inaccessible?

Correct Answer: B

Trigger

Zero-velocity state

Formula / Tool

Acceleration Concept

Quick Execution

Velocity may be zero,

but acceleration may still exist.

Motion can resume immediately.
Trap: Assuming v = 0 means motion has ended permanently.

AC-16

A ball is projected vertically upward. Is downward motion eventually accessible?

Correct Answer: A

Trigger

Reversal accessibility

Formula / Tool

Vertical Motion

Quick Execution

After reaching the highest point,

the ball reverses direction and moves downward.
Trap: Treating upward and downward motion as independent motions.

AC-17

A particle moving with constant positive acceleration can eventually attain a speed greater than its present speed.

Correct Answer: A

Trigger

Future-state accessibility

Formula / Tool

v = u + at

Quick Execution

Positive acceleration increases velocity with time.

Higher speeds become accessible.
Trap: Looking only at the present speed.

AC-18

Two particles move towards each other. Is meeting accessible?

Correct Answer: C

Trigger

Meeting accessibility

Formula / Tool

Relative Motion

Quick Execution

Meeting can occur depending on the initial positions and subsequent motion.
Trap: Confusing possible with guaranteed.

AC-19

A particle is moving away from the origin with increasing speed. Can it later return to the origin?

Correct Answer: B

Trigger

Return accessibility

Formula / Tool

State-Transition Reasoning

Quick Execution

Future acceleration may reverse the motion.

Return remains possible.
Trap: Projecting the current trend indefinitely into the future.

AC-20

A particle moving at 10 m/s is accelerated at 2 m/s². Is a speed of 30 m/s accessible?

Correct Answer: A

Trigger

Target-state accessibility

Formula / Tool

v = u + at

Quick Execution

30 = 10 + 2t

t = 10 s

Therefore 30 m/s is accessible.
Trap: Assuming acceleration changes only displacement and not velocity.

Continue Learning

Explore what happens when motion changes direction and enters new phases.

Pursuit Problems

Catch-up situations and closing-speed analysis.

Reversal of Motion

Turning points, stopping points and direction changes.

Multi-Stage Motion

Motion involving multiple phases and state transitions.

Graph Intelligence

Visualize accessibility and motion through graphs.