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# A trolley of mass 360 kg lying on a horizontal friction less surface. A man of mass 40 kg runs with uniform speed on the trolley a distance of 2 m in $0.5 \;s$. What is the velocity of the trolley relative to the earth?

$\begin {array} {1 1} (a)\;0.8\;m/s & \quad (b)\;0.4\;m/s \\ (c)\;1.6\;m/s & \quad (d)\;2.2\; m/s \end {array}$

Velocity of man (m) relative to trolley
$V_r= \frac{2}{0.5}$
$\quad=4 m/s$
Velocity of trolley (M) in the opposite direction $=V$
$MV=m(V_{r}-V)$
$V= \large\frac{m V_{rel}}{m+M}$
$\quad= \large\frac{40 \times 4}{400}$
$\quad=0.4 m/s$
edited Jun 17, 2014