WORK AND ENERGY
CLASS IX PLZ ANSWER!
A body of mass 20 kg is dropped from 20 m height calculate its kinetic energy just before it touches tge ground.
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height of object = s=20m
mass=20kg
from 3rd eqn. of motion we have to find v^2
2as=V2-U2
and initially u =0
because object at rest
acceleration due to gravity = 9.8m/s^2
so
2*9.8*20=V2-0^2
392m/s = V^2
Kinetic energy = 1/2 MV^2
= 1/2*20*392
=3920J
mass=20kg
from 3rd eqn. of motion we have to find v^2
2as=V2-U2
and initially u =0
because object at rest
acceleration due to gravity = 9.8m/s^2
so
2*9.8*20=V2-0^2
392m/s = V^2
Kinetic energy = 1/2 MV^2
= 1/2*20*392
=3920J
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