Q. 354.4( 15 Votes )

A man drops a 10 kg rock from the top of a 5 m ladder. What is its speed jest before it hits the ground? What is its kinetic energy when it reaches the ground? (g = 10 m/s2)

Answer :

Mass of the rock, m = 10kg

Height from which the rock is dropped, h = 5m


Initial velocity (u) = 0m/s


Let, the final velocity = v m/s


Acceleration due to gravity (g) = 10m/s2


We know,


v2 − u2 = 2as


V2 = 2 × 10 × 5 = 100


Hence, the velocity of the body when it reaches ground is 10 m/s


K.E = 1/2 mv2


=1/2 × 10(10)2


=500 J


Therefore, kinetic energy of the rock = 500J


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