A small block of mass 1 kg starts moving with constant velocity 2 m/s on a smoth long plank of mass 10 kg which is also pulled by a horizontal force `F=10 t` where t is is in seconds and f in newton 's (the initial velocity of the plank is zero)

Relative velocity of plank with to block when acceleration of plank is `4m//s^(2)` wil be

Options

A. zero
B. 10 m/s
C. 6 m/s
D. 8 m/s

Answer

c