Frictional Force

Q.

Give examples of force changing the direction of a moving object.

Q.

An object of mass 2 kg is sliding with a constant velocity of 4 $m{s}^{-1}$ on a frictionless horizontal table. The force required to keep the object moving with the same velocity is

1. 32 N

2. 8 N

3. 2 N

4. 0 N

Q. A horizontal force of 20 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and wall is 0.3. The weight of the block is

1. 20 N
2. 10 N
3. 6 N
4. 3 N

Q.

A box of mass 20 kg is pushed along a rough floor with a velocity 2 $\frac{m}{s}$ and then let go. The box moves 5 m on the floor before coming to rest. What must be the frictional force acting on the box?

1. 4 N

2. 2 N

3. 20 N

4. 8 N

Q.

Which force makes a rolling ball stop on its own on a horizontal surface.

Q.

When a body is stationary

1. There is no force acting on it

2. The combination of forces acting on it balance each other

3. The force acting on it is not in contact with it

4. The body is in a vacuum

Q.

Which of the two push or pull, is easier? Give reason for your answer.

Q.

When a footballer kicks a ball, the ball moves in the direction of the applied force. The footballer also experiences a force on his leg which is equal to the magnitude of the force he exerted on the ball.

1. velocity of ball is proportional to the force acting on it

2. the football player did not hit the ball hard

Q.

A hockey player pushes the ball on the ground. It comes to rest after travelling a certain distance because:

1. The opposing force of friction acts on the ball.

2. The player stops pushing the ball.

3. No unbalanced force acts on the ball.

4. The ball moves only when pushes.

Q. y=(5x^2 +6)× (2x^3 +4) Then dy/dx = ?

Q. Why is there a high friction between two smooth glass pieces?

1. It is due to bond formation between the surfaces.
2. It is due to interlocking between the surfaces.
3. It is due to deformation of the surfaces.
4. It is due to irregularities present on the surfaces.

Q.

A block weighs W is held against a vertical wall by applying a horizontal force F. The minimum value of F needed to hold the block where it is

$assume:\mu <1$

1. Less than W

2. Equal to W

3. Greater than W

4. Data is insufficient

Q.

It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?

Q.

A stone of mass $2kg$ is thrown with a velocity of $20m{s}^{-1}$ across the frozen surface of a lake and comes to rest after travelling a distance of $100m$. Calculate the frictional force between the stone and the ice.

1. $1N$
2. $3N$
3. $2N$
4. $4N$

Q. Question 7 (c)
A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, then calculate:
(c) the force of wagon 1 on wagon 2.

Q.

If first law holds true ., Why does a ball rolling on ground stop on its own

Q.

Can you walk on a frictionless surface ? Why / Why not ?

Q.

When a football player kicks a ball, he experiences a force on his leg which is equal to the force he exerted on the ball.

1. True

2. False

Q.

Velocity versus time graph of a ball of mass $50\mathrm{g}$ rolling on a concrete floor is shown in figure .Calculate the acceleration and frictional force of the floor on the ball.

Q.

Define the term 'Force'.

Q.

When a fast-moving vehicle is suddenly stopped by applying the brake, the force that causes deceleration is exerted by the brake.

1. Due to opposing force of friction

2. Because action and reaction pair are never equal

Q.

When does force of friction come into play?

Q. Does sand spread on table increase or decrease the friction between an object on the table and its surface

Q. Question 5
A passenger in a moving train tosses a coin which falls behind him. It means that motion of the train is
(a) accelerated
(b) uniform
(c) retarded
(d) along circular tracks

Q. What is the cause of friction
is it because of the irregularities in the surfaces or because of some electrostatic forces?

Q.

A ball moving on a table top eventually stops. Explain the reason.

Q.

The direction of force is the direction in which the body is pushed or pulled.

1. True
2. False

Q. State Newton’s third law of motion.

Q. Which of the following forces acts when a surface is sliding over another surface?

1. Rolling friction
2. Static friction
3. Sliding friction
4. Contact friction

Q. A boy walks over a rough surface, then the angle between the force of friction and the instantaneous velocity of the boy is

1. ${90}^0$
2. ${180}^0$
3. ${60}^0$
4. $0^0$