Cause of Friction

Q.

A porter carrying heavy load places a round piece of cloth on his head because it reduces the pressure on his head as the area of contact decreases.

1. False

2. True

Q. Graph between frictional force and applied force is given below. Choose the correct statement among the following

1. Frictional force is directly proportional to the applied force is shown by region $CD$
2. Frictional force is maximum in region $CD$
3. Frictional force is directly proportional to the applied force is shown by region $AB$
4. Region $AB$ is showing dynamic friction and $CD$ is showing static friction

Q. Is friction dependent of surface area of contact ?

Q.

What are the main factors on which friction depends?

Q.

Why Sledges are not provided with wheels?

Q.

Explain why do we find difficult to walk on sand but camel's walk easily on the basis of force and area covered by their feet? 50-70words

Q. A body of mass 5 kg is placed on a rough horizontal surface. If the coefficient of friction is 1/√3, find what pulling should act on the body at an angle 30(degree) to the horizontal so that the body just begins to move.

Q. Why do the heavy vehicles have large number of wheels?

Q.

Explain why snow shoes stop you from sinking into snow?

Q. Friction does not depend on the following factor
A)The nature of the surface. B)The normal reaction
C)Roughness of the surface. D)The area of contact

Q. The hardest naturally occurring substance found on Earth is

1. Iron
2. Sodium
3. Diamond

Q. Does friction exist in space?

Q.

The handle of a cricket bat or a badminton racquet is usually rough. Explain the reason.

Q. Prove that 5 is a irrational number.

Q.

How does air cushions reduce friction?

Q. Why do skiers use long and flat skies on the snow?

Q.

State two factors that directly affect the force of friction?

Q.

The force acting between two surfaces moving over each other is __________.

Q.

Why are nails made very thin at one end and somewhat thick at the other end ?

Q.

1)What is limiting friction

Q.

A force applied by directly touching an object is called a _________

Q. What is relative motion.
What is frictional force

Q. Question 27
Two rods of the same weight and equal length have different thickness. They are held vertically on the surface of sand as shown in Fig.11.9. Which one of them will sink move? Why?

Q. The causes of friction are molecular adhesion, interlocking of surface irregularities and plowing effect.

1. True
2. False

Q.

Friction causes _______ of energy.

Q.

Assertion (A): Skiers use short flat skies to slide over the snow.
Reason (R): They can slide easily on the snow because larger the area of contact, the lesser will be the pressure on the snow.

1. A is correct and R is the correct reason for A.

2. A is correct but R is not the correct reason for A.

3. A is incorrect but R is correct.

4. Both A and R is incorrect.

Q.

Explain the statement

The rear side of truck is provided with double wheels.

Q.

A solid weighs 300n. Calculate the pressure exerted by solid when it is kept on a glass surface if the area of contact is 400cm^2.

Q.

While travelling on a rickshaw, you might have experienced that if the seat cover is very smooth, you tend to slip when brakes are applied suddenly. Explain.

Q.

Does friction depends on the smoothness or the roughness of the surfaces in contact?