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When a mass 8kg is just released,its kinetic energy when it touches the ground is(pulley is weightless and frictionless)

When a mass 8kg is just released,its kinetic energy when it touches the ground is(pulley is weightless and frictionless)

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downey zer
73 Points
6 years ago
when 8 kg will move down by 7m ,4kg has to go up by 7m 
total work done on system by gravity = 8g*7-4g*7=28g
this is equal to the total change in kE of the system 
let the velocity of 8kg be v since 4kg is connected to 8kg by string therefore 4kg must also have velocity v
total kE = 1/2(4+8)v2
KE of 8kg= 1/2(8)v2
 KE of 8kg/ Total KE=2/3
But total kE = 28g
therefore KE of 8kg=2/3*28g=56/3g
hope that helps. please approve the answer if it did

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