Question

96. A body is in contact with the vertical
front part of the truck. The coefficient of
friction between the body and the truck is
u. The minimum acceleration with which
the truck should travel so that the body
does not fall down is
(NEET 2010)
1) u/g 2) ug )g/4) upg

Answer 1

Answer:

Suppose,when the truck moves with acceleration

a

,the body suddenly feels a backward force of

m

a

(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

m

a

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)

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So,

N

=

m

a

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 = μN=μ

ma

Hence,

ma=mg

or,

a=gμ

Answer 2

Explanation:

Let the mass of the body be 'm'

Friction = uN

Where N = uma

'a' is the acceleration of the truck.

For this case the friction should be equal to the weight of the body. And the normal reaction force is the force of friction exerted on the body by the truck.

So,

= N = mg

= uma = mg

= ua = g

= a = g/u

So the minimum acceleration of the truck should be g/a.