FrictionMediumBloom L1
Question
The coefficient of friction between the block and plank is μ and ground is smooth. The value of µ is such that block becomes stationary with respect to plank before it reaches the other end. Then which of the following statement is incorrect.
Options
A.The work done by friction on the block is negative.
B.The work done by friction on the plank is positive .
C.The net work done by friction is negative.
D.Net work done by the friction is zero.
Solution
Sol.
mv0 = (M + m)v ⇒ v = $\frac{mv_{0}}{(M + m)}$
$(\Delta K)_{system} = \frac{1}{9}(M + m)u^{2} - \frac{1}{2}mu_{0}^{3} = \frac{1}{9}(M + m)\left\lbrack \frac{mv_{0}}{M + m} \right\rbrack^{2} - \frac{1}{2}mv_{0}^{2}$
$= \frac{1}{2}\left( \frac{m^{2}}{M + m} \right)u_{0}^{2} - \frac{1}{2}mv_{0}^{2} = \frac{1}{9}mv_{0}^{2}\left\lbrack \frac{m}{M + m} - 1 \right\rbrack$
∴ Total work of friction is
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