Work Energy And Power Question 221

Question: Calculate the K.E and RE. of the ball half way up, when a ball of mass 0.1 kg is thrown vertically upwards with an initial speed of $ 20m{s^{-1}} $ .

Options:

A) $ 10J,20J $

B) $ 10J,10J $

C) $ 15J,8J $

D) $ 8J,16J $

Show Answer

Answer:

Correct Answer: B

Solution:

[b] Total energy at the time of projection

$ =\frac{1}{2}mv^{2}=\frac{1}{2}\times 0.1{{( 20 )}^{2}}=20J $

Half way up, P.E. becomes half the P.E. at the top i.e. $ P.E.=\frac{20}{2}=10J $

$ \therefore K.E. =20-10=10J $



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