Friction

Angle of repose is equal to

When a person walks on a rough surface the frictional force exerted by the surface on the person is opposite to the direction of motion.

The distance travelled by a body before coming to rest, if its initial velocity is $36 \mathrm{km}/\mathrm{hr}$ and coefficient of friction between the body and surface is $0.2$, is  _____.

State the laws of limiting friction? How would you verify them.

Define angle of repose and angle of friction. Establish relation between them.

A pick-up truck of $3000 \mathrm{kg}$ going at $25 \mathrm{m}/\mathrm{s}$ has its breakes locked and starts skidding with the engine shut off. If the coefficient of friction is $0.2$ how far will the truck travel before stopping?

The coefficient of friction between a block of wood of mass $20 \mathrm{kg}$ and table surface is $0.25$. What force is needed to give it an acceleration of $0.2 \mathrm{m}/{\mathrm{s}}^2$? Take $g=9.8 m/s^2$ 

 A student holds a book of mass $1 \mathrm{kg}$ between his hands. Each hand exerts horizontally a force of $49 \mathrm{N}$. Find the coefficient of static friction between the hand and the book.

What are the causes of sliding friction?

Why is it easier to roll a barrel than push it along a road?

Why does lubrication reduce friction?

State the laws of friction.

Give two examples where friction is artificially increased.

What are the methods for reducing friction?

What is the minimum stopping distance of a car of mass $m$ moving with speed $g$ along a level road if the coefficient of static friction between tyres and road is $\mu$.

Explain how friction is a necessary evil.

Which of the following should be decreased to transport a massive cylinder by rolling on a flat surface ?

Aeroplanes and jets are streamlined to reduce

The tyres are made of rubber and not of iron because