please answer this..............

Asked by  | 1st Aug, 2009, 04:32: PM

Expert Answer:

 

The stone is thrown vertically upwards, so velocity is upwards, but the acceleration due to gravity is downwards,

v = u + at = u + (-g)t = 9.8 m/s + (-9.8 m/s2) (0.5 s) = 4.9 m/s

{ u = initial velocity, v = final velocity, a = acceleration, t = time, g = acceleration due to gravity, m = mass}

Hence KE = mv2/2 = (0.4 kg)(4.9 m/s)2/2 = 4.8 J

Initial KE = (0.4 kg)(9.8 m/s)2/2 = 19.2 J

Initial KE decreases, and the decreased amount is converted into PE.

Hence PE = Initial KE - Final KE = 19.2 J - 4.8 J = 14.4 J 

So the answer is KE energy is 4.8 J and PE is 14.4 J after half second.

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TopperLearning

Answered by  | 1st Aug, 2009, 10:10: PM

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