Question

A body slipping on a rough horizontal plane moves with a deceleration of $4.0m/{s^2}$ What is the coefficient of kinetic friction between the block and the plane?

Answer 1

We know that friction is a contact force along the tangent to the contacting the surfaces to destroy the relative motion between them. When objects are placed on each other and the system slides down on a horizontal road, a force is acting vertically and horizontally on the system. Then using the above determines its coefficient of kinetic friction.

Formula:
$f = \mu N$
Where $\mu$ is coefficient of friction, $f$ is the frictional force, $N$ is the Normal force.

Complete step by step answer:
• Friction is the force in which opposition comes between two surfaces so as to impede the relative motion between them.
• Friction is regarded as an electromagnetic force. Friction can also be due to the forces among molecules at close proximities.
• The surface will slip on each other without opposition in the absence of friction. This may be producing a dangerous motion.
• Polishing the machine, using lubricants on the machine, using ball bearing, streamlining can reduce friction.
• The resistance by a body in a static condition while it tends to be move under the action of external force
• This resistance is called static frictional force. The ratio of limiting friction (maximum static friction) to normal reaction is called coefficient of static friction. It is a unit less quantity.

Frictional force is given by
$F = ma$
Here $a = 4m/{s^2}$
Then $F = 4mN$
The normal force is equal to $mg$
Then we know $F = \mu N$
$\mu = \dfrac{{4m}}{{mg}} = \dfrac{4}{{10}} = 0.4$

Hence coefficient of kinetic friction is $0.4$.

Note: The surfaces will slip on each other without opposition in the absence of friction. This may be producing a dangerous motion. Polishing the machine, using lubricants on the machine, using ball bearing, streamlining can reduce friction. The way that is effective to reduce friction is to place a thin cushion of air maintained between the solid surfaces in relative motion.