Question

Five objects of different masses are simultaneously released vertically downwards from height $h$ (in air). Which physical quantity associated with the objects will change at the instant they strike the ground? (Neglect air resistance.)

• A. Momentum
• B. Time
• C. Acceleration
• D. Velocity

Hint:

In free fall without air resistance, velocity is mass-independent but momentum is not.

Answer 1

The Correct Option is A

Step 1: Velocity at the instant of impact.
All objects fall with the same acceleration $g$, so they reach the ground with the same velocity.

Step 2: Momentum dependence.
Momentum is given by:
\[ p = mv \] Since masses are different and velocity is same, momentum differs for each object.

Step 3: Analyze other quantities.
Time of fall, acceleration, and velocity are the same for all objects.

Step 4: Conclusion.
Momentum is the physical quantity that changes.