 Physics
5 August, 20:51

# A Stone of mass 20kg fall from a height 5m. what is the time take to reach the ground? 2. The average kinetic energy of body (neglect energy loss and take gravity 10m/s2)

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1. 5 August, 22:00
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a) t = 1second

b) KE = 1000Joules

Explanation:

According to equation of motion,

S = ut+1/2at² where

S is the distance or height of fall = 5m

u = initial velocity = 0m/s²

a = + g = acceleration due to gravity = 10m/s²

Substituting the values in the formula to get the time we have,

5 = 0+1/2 (10) t²

5 = 5t²

t² = 1

t = 1second

Time taken by the stone to reach the ground is 1second

b) Kinetic energy is the energy possessed by a body by virtue if its motion.

KE = 1/2MV² where m is the mass of the body and v is the velocity.

Given mass = 20kg

To get the velocity, we will use the equation of motion,

v = u + at

v is the final velocity

u is the initial velocity = 0m/s

a = + g = 10m/s

t = time = 1second

v = 0+10 (1)

v = 10m/s

KE = 1/2*20*10²

KE = 10*100

KE = 1,000Joules
2. 5 August, 22:16
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Total time taken is 980seconds