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CBSE Class 9 Answered

a stone of mass 3kg is falling from rest from the top ofa hill.what will be its K.E. after 3s.if the hill is 100m high,what will be its K.E.just before hitting the ground.
Asked by ganga kaushik mangena | 27 Feb, 2011, 05:34: AM
Expert Answer
Dear student
Given mass= 3 kg
u =0
t=3 s
using the equation, v=u+at
v= 10 x 3 = 30m/s
KE after 3 sec = (1/2)x 3 x (30)^2 J
 
Given h = 100m
Velocity just before striking the ground,
v^2-u^2 = 2ah
v^2 = 2 x 100 x 10=2000
v = m/s
So KE= (1/2)x 3 x (20√5)^2 J
 
Regards
Team
Topperlearning
Answered by | 27 Feb, 2011, 10:16: PM

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