Static Friction

Q. 37 A uniform ladder of length 3.25 m and weighing 250 N is placed against a smooth verticalwall with its lower end 1.25 m from the wall. If coefficient of friction between the ladderand the floor is 0.3, then, find the frictional force acting on the ladder at the point of contactbetween ladder and floor

Q.

A car turns a corner on a slippery road at a constant speed of 10 m/s. If the coefficient of friction is 0.5, the minimum radius of the arc in meter in which the car turns is

1. 20

2. 10

3. 5

4. 4

Q.

What minimum amount of force is required to move a 10kg block kept on a horizontal surface. Given (${\mu }_s$=0.5), (${\mu }_k$=0.4) If the block was already moving then what would be the minimum force required to maintain its velocity at a constant value?

1. 0N, 40N

2. 50N, 0N

3. 50N, 40N

4. 40N, 50N

Q.

A block of mass 10 kg slides with velocity of 10 m/s on a rough horizontal surface. It comes to rest after covering a distance of 50 meters. Find the frictional force.

1. 100N

2. 1N

3. 10N

4. 5N

Q. A 13m ladder is placed against a smooth vertical wall with its lower end 5m from the wall. what should be the minimum coefficient of friction between ladder and floor so that it remains in equilibrium.

Q. a chain of mass M and length L is placed on table, such that only a part of it is on table and remaining part hangs in air.If the coefficient of friction between chain and table is u , find the maximum length of chain that can hang in air without sliding

Q. a uniform rod of mass M pulled by forve F on smoothbsurface the value of tensionT in the rod variesbwithbthe dis†an ce X from the force end is according to the gra

Q.

In a rotor, a hollow vertical cylindrical structure rotates about its axis and a person rests against the inner wall. At a particular speed of the rotor, the floor below the person is removed and the person hangs resting against the wall without any floor. If the radius of the rotor is 2 m and the coefficient of static friction between the wall and the person is 0.2, find the minimum speed of rotor at which the floor may be removed. Take g = 10 m/$s^2$.

1. 2 m/s

2. 10 m/s

3. 20 m/s

4. None of these

Q.

Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The stone slides with the door and the door gets closed. However, if you sandwich a 20 gm piece of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter piece of wood is able to keep the door open while the heavy stone fails. Assume coefficient of friction between stone and ground and wood and ground are the same.

1. (a)Surface area of contact between wood and door is less

2. (a)There is no horizontal force on the wood by the door

3. Limiting friction will increase as the horizontal force on the block by the ground will increase

4. None of these

Q.

A boy of mass M is applying a horizontal force to slide a box of mass M' on a rough horizontal surface. The coefficient of friction between the shoes of the boy and the floor is μ and that between the box and the floor is μ'. In which of the following cases it is certainly not possible to slide the box given the boy is not slipping

1. $\mu <{\mu }^{\prime }$ , M<M'

2. $\mu >{\mu }^{\prime }$ , M>M'

3. $\mu <{\mu }^{\prime }$ , M>M'

4. $\mu >{\mu }^{\prime }$ , M<M'

Q.

A block of mass M is being pulled along rough horizontal surface. The coefficient of friction between the block and the surface is $\mu$. If another block of mass M/2 is placed on the block and it is again pulled on the surface, the coefficient of friction between the block and the surface will be

1. 

2. 2

3. 

4. 

Q. Friction acting on a body when it is at rest relative to the surface is known as

1. static friction
2. kinetic friction
3. limiting friction
4. rolling friction

Q.

10kg block is kept on a horizontal surface and Ram is trying to pull it with a force of 5N, Given coefficient of static friction is 0.2 and coefficient of Kinetic friction n(μK) = 0.1 Which of these statements is/are correct.

1. He will succeed in pulling the block

2. He won't succeed in pulling the block as kinetic friction on block will be 30N

3. He won't succeed in pulling the block as friction on block will be 10N

4. He won't succeed in pulling the block as force applied is only 5N whereas friction force can resist up to 20N.

Q. unit and dimension of coefficient of rolling friction is--

Q. A window scrubber is used to brush up a vertical window as shown in figure.The brush weight 12 N and coefficient of friction of 0.15. Calculate minimumvalue of F required to scrub the window.(A)(B)15 N10.2 N53(D)18.1 N(C)16.9 N33

Q. 39.A small body slides down from a height h and passes into a circle of radius h/2 as shown. Friction is negligible. What is the velocity of the body at the h

Q. A uniform disc is released from the top of a rough inclined plane of angle beta and height h the coefficient of friction between the disc and the plane is tan(beta)/4 .the speed of centre of mass of the disc on reaching the bottom will be in terms of height of inclined plane

Q. nta uniform ladder of length 3.25m and weighing 250N is placed againsts a smooth vertical wall with its lower end 1.25m from the wall. If coefficient of friction between the ladder and the floor is 0.3 then, find the frictional force acting on the ladder at the point of contact between ladder and floorn

Q.

A 10kg block is kept on a horizontal surface and Ram is trying to pull it with a force of 5N, Given coefficient of static friction is 0.2 and coefficient of Kinetic friction n(μK) = 0.1 Which of these statements is/are correct.

1. He will succeed in pulling the block

2. He won't succeed in pulling the block as kinetic friction on block will be 30N

3. He won't succeed in pulling the block as friction on block will be 10N

4. He won't succeed in pulling the block as force applied is only 5N whereas friction force can resist up to 20N.

Q.

On what parameters coefficient of friction depends?

Q. 73.uniform ladder of length 3.25m and weighing 250N is placed againsts a smooth vertical wall with its lower end 1.25m from the wall. If coefficient of friction between the ladder and the floor is 0.3 then, find the frictional force acting on the ladder at the point of contact between ladder and floor

Q.

If the coefficient of friction between all surfaces (fig.) is 0.4, then find the minimum force F to have equilibrium of the system.

1. 50 N

2. 62.5 N

3. 150 N

4. 31.25 N

Q.

A block is placed on a rough floor and a horizontal external force F is applied on it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them. (taking f on Y and F on X axis)

1. There is a small kink on the graph

2. (a)The graph is a straight line of slope

3. The graph is a straight line parallel to the F-axis

4. The graph is a straight line of slope for small F and a straight line parallel to the F-axis for large F

Q. Two bodies of masses 5 Kg and 10 Kg in contact with each other rest on a table against a rigid wall. The coefficient of friction between the bodies and the table is 0.15. A force of 200N is applied horizontally to A. What are (a) the reaction of the partition (b) action reaction forces between A and B. What happens if wall is removed? Does t

Q. can work done by friction ever be positive?

Q. In a situation the contact force by a rough horizontal surface on a body placed on it has constant magnitude. If the angle between this force and the vertical is decreased, the frictional force between the surface and the body will
(a) increase
(b) decrease
(c) remain the same
(d) may increase or decrease.

Q. The SI unit of static coefficient of friction is

1. N
2. $\frac{N}{m}$
3. Nm
4. it is unit less

Q. A block of mass $1kg$ is projected from the lowest point up along the inclined plane, if $g=10m/s^2$, the retardation experienced by the block is

1. $\frac{15}{\sqrt{2}}m/s^2$
2. $\frac{5}{\sqrt{2}}m/s^2$
3. $\frac{10}{\sqrt{2}}m/s^2$
4. zero

Q. A uniform chain of length $L$ has one of its ends attached to the wall at point A, while $\frac{3L}{4}$ length of the chain is lying on the table as shown in figure. Then, minimum co-efficient of static friction between table and chain, so that the chain remains in equilibrium is

1. $\frac{1}{3}$
2. $\frac{1}{4}$
3. $\frac{3}{4}$
4. $\frac{1}{5}$

Q. Mass of block A is $100\text{kg}$ and that of block B is $200\text{kg}$. As shown in figure, the block A is attached to a string tied to the wall. The coefficient of static friction between blocks A and B is $({\mu }_s{)}_A=0.2$ and the coefficient of static friction between block B and floor is $({\mu }_s{)}_B=0.3$. Then calculate the minimum value of force $F$ required to move the block B. $(g=10{\text{m/s}}^2)$

1. $980\text{N}$
2. $1000\text{N}$
3. $1100\text{N}$
4. $1200\text{N}$