A van accelerates uniformly down an inclined hill going from reast to `30m//s` in `6s`. During the acceleration , a toy of mass `m=0.1kg` hangs by a light string from the van's ceiling . The acceleration is such that string remains perpendicular to the ceiling. `(` Take `g=10m//s^(2))`

The friction force on the van is

Options

A. Zero
B. `mgcos theta`
C. `mg sin theta`
D. `mg tan theta`

Answer

A

Explanation

Acceleration of the van `=(30)/(6)=5 m//s^(2)`
`g sin theta =a`
`rArr sin theta =(1)/(2)`
`rArr theta=30^(@)`
Since accelerated the van is `g sin theta `, there is no friction.