Kinetic Friction

Q. A uniform chain of length L and mass M is lying on a smooth table and one fourth of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, then the work required to pull the hanging part on the table is

Q. 33/ A block is projected with speed 20 m/s on a roughhorizontal surface. The coefficient of friction (u)between the surfaces varies with time () as showin figure. The speed of body at the end of 4 secondwill be (g = 10 m/s2)0.50.3ts)2(1) 2 m/s(2) 5 m/s(3) 7.2 m/s(4) 9.5 m/s

Q. In the figure shown coefficient of friction between8 kg block and surface is zero and coefficient offriction (both static and kinetic) between the blocksis 0.4. A force of 20 N is applied on 8 kg block asshown The acceleration of 4 kg mass is(g 10 m/s24 kg20 N8 kg7

Q. Define angle of Friction.

Q. A cylinder of mass 10kg is sliding on a plane with initial velocity 10m/s. If the coefficient of friction between the cylinder and the floor is 0.5, then what dis†an ce will it cover before stopping?

Q. A block of mass 10 kg is placed on a rough horizontal surface of coefficient of friction 0.5. The minimum force required to move the block is (g = 10 m/s^2)

Q.

A scooter starting from rest moves with a constant acceleration for a time $\Delta$ $t_1$, then with a constant velocity for the next $\Delta$ $t_2$, and finally with a constant deceleration. A person of mass 50 kg on the scooter, behind the driver manages to stay at rest with respect to the scooter without touching any other part. The force exerted by the seat on the man is

Take g=10m/ $s^2$

1. less than 500 N throughout the journey

2. more than 500 N throughout the journey

3. > 500 N for time and , and 500 N for ,

4. 500 N throughout the journey

Q.

Find out acceleration of the block. Initially the block is at rest.

${\mu }_s$ = 0.5

${\mu }_K$ = 0.3

1. 0.1 m/

2. 2.1 m/

3. 1 m/

4. 2 m/

Q. Mark the correct statements about the friction between two bodies.
(a) Static friction is always greater than the kinetic friction.
(b) Coefficient of static friction is always greater than the coefficient of kinetic friction.
(c) Limiting friction is always greater than the kinetic friction.
(d) Limiting friction is never less than static friction.

Q.

The maximum speed at which a car can turn round a curve of 40 m radius on a level road is: (Given: coefficient of friction between the tyres and road is 0.5)

1. 14 m/s

2. 21 m/s

3. 26 m/s

4. 20 m/s

Q. 87.A person of mass 72kg sitting on ice pushes a block of mass of 30kg on ice horizontally with a speed of 12m/s.the coefficient of friction between the man and ice and between block and ice in 0.02.if g=10m/S2, the distances between man and the block, when they come to rest is a)360m b)10m c)350m d)422.5m

Q.

A body of mass 10 kg is slipping on a rough horizontal plane and moves with a deceleration of 4.0 m/ $s^2$. What is the magnitude of frictional force?

1. 40N

2. 20N

3. 100N

4. Data insufficient require coefficient of kinetic friction

Q. A block slides down an inclined plane of inclination ${30}^{\circ }$ with a constant acceleration $g/4$ .Coefficient of kinetic friction is given by $\frac{1}{N\sqrt{3}}$. Then, the value of $N$ is

Q. A small block of mass m is kept on a rough inclined surface of inclination θ. The block does not slide on the surface. The work done by friction on block in time t will be a) Zero b) -mgvt sinθ.cosθ c) mgvt sin ²θ d) mgvt cos2θ

Q.

A body of mass m rises to a height h = R/5 from the earth's surface where R is earth's radius. If g is acceleration due to gravity , the increase in PE is

1. 5mgh/6

2. 6mgh/7

3. mgh

4. 4mgh/5

Q. Block A of mass 2 kg is placed over a block B of mass 8 kg. The combination is placed on a rough horizontal surface. If g 10 ms^2, coefficient of friction between B and floor 0.5, coefficient of friction between A and B= 0.4 and a horizontal force of 10 N is applied on 8 kg block, then calculate the force of friction between A and B

Q. \begin{array}{lc}Two bodies A and B of mass 5kg and 10 kg are in contact with each other rest on a table against & a rigid wall. the coefficient of friction between the bodies and the table is0.2.when theforce of200N.& is applied, how to calculate normal reaction b/w wall and blacks, between 2 blocks will not weight of blocks contribute to that normal reaction ?(bodies against rigid wall)

Q. 3. A body slides down from rest from the top of a 6.4m long rough plane inclined at 30^° with the horizontal .find the time taken by the blocl in reaching the bottom of the plane.take coefficient of kinetic friction=0.2and g=9.8ms2

Q. lus-1-Two blocks of masses 2 mand m are shown in the figure. Now the string between the blocks is suddenly broken. The acceleration of the block A and B respectively at that instant are: 1) gand g (2) g and g/2 3) g/2 and g(3

Q.

A 1.0 kg block collides with a horizontal light spring of force constant 2 $\frac{N}{m}$. The block compresses the spring 4m from the rest position. Assuming that the coefficient of kinetic friction between the block and the horizontal surface is 0.25, what was the speed of the block at the instant of collision?

1. 52

2. 

3. 25

4. none of these

Q. Three blocks A, B and C of masses 2 kg, 3 kg and4 kg are placed as shown. Coefficient of frictionbetween A and B is 0.5 and that between B and Cis0.1. The surface is frictionless. The maximum forceF that can be applied horizontally onto A such thatthe three blocks move together isA HAB= 0.5= 0.1F>ВuBcсПТFrictionlessLL

Q. A block of mass 2 kg is pushed against a rough vertical wall with a force of 40 N, coefficient of static friction being 0.5. Another horizontal force of 15 N, is applied on the block in a direction parallel to the wall. Will the block move? If yes, in which direction? If no, find the frictional force exerted by the wall on the block.

Q.

A block placed on a horizontal surface is being pushed by a force F making an angle $\theta$ with the vertical. If the friction coefficient is $\mu$, how much force is needed to get the block just started.

1. F=

2. F=mg(cos - sin)

3. F=mg(sin - cos)

4. F=

Q. Figure (8-E7) shows a spring fixed at the bottom end of an incline of inclination 37°. A small block of mass 2 kg starts slipping down the incline from a point 4⋅8 m away from the spring. The block compresses the spring by 20 cm, stops momentarily and then rebounds through a distance of 1 m up the incline. Find (a) the friction coefficient between the plane and the block and (b) the spring constant of the spring. Take g = 10 m/s².
Figure

Q. A uniform chain of lenth L and mass M is lying on a smooth table and one third of its length is hanging down over the edge of the table. If g is acceleration due to gravity, the minimum work required to pull the hanging part of the chain on the table is

Q.

A 5 kg block kept on a frictionless horizontal plane is being acted upon by a 10 N force as shown. Find the acceleration of the block.

1. Data insufficient

2. 1 m/

3. 2 m/

4. 5 m/

Q. A block of mass $10kg$ is pulled at constant speed on a rough horizontal surface by a force of $19.6N$. The coefficient of friction is

1. $0.1$
2. $0.2$
3. $0.3$
4. $0.4$

Q. Q 23/30 If a body of mass m is raised to height 2 Rfrom the earths surface, then the change in potentialenergy of the body is (R is the radius of earth)

Q. 53.Ratio of acceleration of block A(10kg) placed on smooth incline, with block B(20kg) placed on rough incline is 2:1. Find coefficient of kinetic friction between block B and incline.

Q. A block is placed on a rough floor and a horizontal 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.
(a) The graph is a straight line of slope 45°.
(b) The graph is a straight line parallel to the F-axis.
(c) The graph is a straight line of slope 45° for small F and a straight line parallel to the F-axis for large F.
(d) There is a small kink on the graph.