Question

A stone of 5 kg drops from a height of 100 M.
Calculate its time to reach the ground
also calculate the velocity with which it hits
the ground. Let
,
g = 10 m/s square​

Answer 1

*Correct Question:-

A stone of mass (50kg) is dropped from a height of 100 m. What is the KE at the bottom and the velocity of the stone at the bottom? Also, can you calculate the PE of the stone at the top and 50m above the ground?

Given:

mass m of stone = 50 kg, height h from ground = 100 m,

Questions:

KE at 0 m = ?, velocity at 0 m = ?, PE at 100 m = ?, PE at 50 m = ?

Equations to use:

v^2 – u^2 = 2gh

PE at 100 m = mgh

KE at 0 m = 1/2 * mv^2 = PE at 100 m

Solving for the initial velocity u of the

stone at 100 m

u = 0 m/s

Solving for the velocity v of the stone at

0 m

v^2 – u^2 = 2gh

v^2 – 0^2 = 2 * 9.8 m/s^2 * 100 m

v^2 = 19.6 m/s^2 * 100 m

v^2 = 1960 (m/s)^2

v = sqrt of 1960 (m/s)^2

v = 44.27 m/s

Solving for the KE of the stone at 0 m

KE = 1/2 mv^2

KE = 1/2 * 50 kg * 1960 m^2/s^2

KE = 25 kg * 1960 m^2/s^2

KE = 49,000 joules

Solving for PE of the stone at 100 m

PE at 100 m = KE at 0 m

PE at 100 m = 49,000 joules

Solving for PE of the stone at 50 m

PE at 50 m = 49,000 joules – mgh

PE at 50 m = 49,000 J – (50 kg * 9.8 m/s^2 * 50 m)

PE at 50 m = 49,000 J – 24,500 J

PE at 50 m = 24,500 joules