Kinetic Friction

Q.

Why rolling friction is less than sliding friction and is really friction is not dependent on the contact area?

Q. State two factors which directly affect the force of friction.

Q.

Definition of sliding friction.

Q.

Why is it difficult to climb up a greasy pole?

Q.

Starting from rest, the time taken by a body sliding down on a rough inclined plane at ${45}^{°}$ with the horizontal is twice the time taken to travel on a smooth plane of same inclination and same distance. Then, find the coefficient of kinetic friction.

1. $0·25$

2. $0·33$

3. $0·50$

4. $0·75$

Q.

Force of friction arises due to the between two surfaces.

Q.

The limiting friction of a body independent of its ……………………

Q. List three disadvantages of friction.

Q. It is difficult to open an inkpot with greasy or oily hands. Explain.

Q.

Sliding friction is ___________ than the static friction.

Q. Statement 1: Sliding friction is less than the maximum value of static friction.

Statement 2: Frictional force acts only when the surfaces are in contact.

1. Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1.
2. Both statements 1 and 2 are correct and statement 2 is not the correct explanation of statement 1.
3. Statement 1 is correct but statement 2 is incorrect.
4. Statement 1 is incorrect but statement 2 is correct.

Q. What is damped oscillator?

Q. Fill in the blanks:​

Friction causes _______ of moving parts of a machine.​

Q. Fill in the blanks:​

We use ball bearings to ______ friction.​

Q. Write true or false for the following statement:​

A wet oily road offers more friction than a dry rough road.​

Q.

You spill a bucket of soapy water on a marble floor accidentally. Which of the following statement is correct?

1. It will be easier to walk after the spilling.

2. It will be difficult to walk after the spilling because the force of friction increases.

3. It will be difficult to walk after the spilling because the force of friction decreases.

4. It will be easier to walk after the spilling because the force of friction increases.

Q. Define sliding friction.

Q.

We use ball bearings to _______________ the friction.

Q.

On applying a force, a block starts sliding on a fixed rough horizontal surface as shown below. What is the direction of frictional force acting on it?

1. Vertically upwards

2. Towards right

3. Vertically downwards

4. Towards left

Q. The friction that exists between a surface sliding over another is called ..................

Q. Friction can be reduced on a road by _______.

1. making the surface dry
2. making the surface wet
3. making the surface rubbery

4. digging the surface

Q. Give three examples to illustrate that friction is a necessary evil.

Q. The coefficient of limiting friction between the surfaces of contact is the ratio of the ....................... friction to the normal reaction.

1. Limting
2. sliding
3. rolling
4. any of these

Q. It is difficult to move a cycle while applying brakes because:

1. rolling friction opposes motion on road
2. sliding friction opposes motion on road
3. rolling friction is more than sliding friction
4. sliding friction is more than rolling friction

Q. Explain why sliding friction is less than static friction?

Q. Which of the following statements about friction is true?

1. Frictional force can accelerate a body
2. Sliding friction is always greater than rolling friction
3. Friction can be reduced to zero
4. Frictional force is proportional to the area of contact between the two surfaces

Q. Statement I : The force of friction experienced while walking on a wet floor is lesser than the force of friction while walking on a dry floor.
Statement II :Greater the weight of a moving body on a surface, greater the force of friction it suffers due to the surface.

1. Statement I is correct and
   statement II is incorrect.
   
2. Both the statements
   are correct.
   
3. Both the statements
   are incorrect.
   
4. Statement I is incorrect
   and statement II is correct.
   

Q. Sliding friction is another name for ______ friction.

1. smooth
2. rolling
3. non static
4. kinetic

Q. A given object takes $n$ times as much times to slide down a ${45}^o$ rough incline as it takes to slide down a perfectly smooth ${45}^o$ incline. What is the coefficient of kinetic friction between the object and the incline?

Q. The motion of a block sliding down a frictionless ramp can be described as motion with

1. A constant speed, independent of the slope of the ramp
2. A constant speed that depends on the slope of the ramp
3. An acceleration which increases as the block slides
4. A constant acceleration less than $10m/s^2$
5. A constant acceleration greater than $10m/s^2$