Work Energy And Power Question 169

Question: A mass of 20 kg moving with a speed of 10m/s collides with another stationary mass of $ 5kg. $ As a result of the collision, the two masses stick together. The kinetic energy of the composite mass will be [MP PMT 2000]

Options:

A) 600 Joule

B) 800 Joule

C) 1000 Joule

D) 1200 Joule

Show Answer

Answer:

Correct Answer: B

Solution:

$ m_1v_1+m_2v_2=(m_1+m_2){v _{sys\text{.}}} $

$ 20\times 10+5\times 0=(20+5)\ {v _{sys\text{.}}} $

therefore $ {v _{sys\text{.}}}=8m/s $

K.E. of composite mass $ =\frac{1}{2}(20+5)\times {{(8)}^{2}}=800J $



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