Question

A body is in contact with the vertical front part of the truck. The coefficient of friction between the body and the truck is `mu` . The minimum acceleration with which the truck should travel so that the body does not fall down is ?

(1)`mu`/g
(2)`mu`g
(3)g/`mu`
(4)`mu^2`g

Answer 1

`3`

Explanation:

Suppose,when the truck moves with acceleration `a`,the body suddenly feels a backward force of `ma` (where, `m` is the mass of the block,which gets balanced by the normal reaction `N` of the truck on the body. (thinking from non inertial frame of reference,i.e considering we are on the body,so we will see the body to be at rest,so due to the motion of the truck `ma` force is acting backwards,as the body tends to fall on back,which is being balanced by the normal reaction of the truck on the body)

.

So, `N=ma`

Now,the body will not fall only when,its weight will be just balanced by frictional force acting between the body and the truck.

So,here frictional force acting =`muN=muma`

Hence, `muma=mg`

or, `a=g/mu`