In a situation the contact force by a rough horizontal surface on… - Vidyadip

MCQ

In a situation the contact force by a rough horizontal surface on a body placed on it has constant magnitude. If the angle between this force and the vertical is decreased, the frictional force between the surface and the body will:

A
Increase.
✓
Decrease.
C
Remain the saint.
D
May increase or decrease.

✓

Answer

Correct option: B.

Decrease.

Explanation:

According to the first law of limiting friction,

$\text{f}=\mu\text{N}$

where f is the frictional force

N is the normal reaction force

$\mu$ is the coefficient of static friction

and

$\text{N = mg}-\text{F}\cos\theta$

where m is the mass of the body

F is the contact force acting on the body

If we decrease the angle between this contact force and the vertical, then $\text{F}\cos\theta$ increases and the normal reaction force (N) as well as the frictional force (f) decrease.

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