Question

An iron cannonball and a bowling ball are dropped at the same time from the top of a building. At the instant before the balls hit the sidewalk, the heavier cannonball has a greater?

A.velocity.
B.aceleration.
C.kinetic energy.
D.All of these are the same for the two balls.

Answer 1

C) kinetic energy

When an object is held at some height, It experiences gravitational pull. But, as it is held the Gravitational pull is stored as a potential energy equal to the product of Mass (m) , Acceleration due to gravity (g) and Height (h) at which the object exists.

P.E = mgh

As it is dropped, the potential energy is converted into Kinetic energy and it is given by

K.E = ½∗m∗v2

By the principle of conservationof energy

P.E = K.E

Thus, mgh = ½∗m∗v2
Therefore, Velocity v=√2gh is independent of mass 'm' of the object. So, No matter how heavy or light the object is, its speed only depends on Height of drop 'h' (as long as 'g' is constant).

so that accelertion and velocity are same but KE is different for heavier mass it will be higher