Kinetic Friction

Q. Consider a raindrop falling through a cloud of tiny water droplets. Some of these tiny droplets get attached to this raindrop as it falls increasing its mass. Assume constant growth in the mass of the raindrop as a function of distance x of fall. Find out the acceleration of the raindrop assuming it to be constant.

1. g/6
2. g/4
3. g/3
4. g/2

Q. The direction of Kinetic friction at the given instant
1) On the block, exerted by the ground
2) On the ground, exerted by the block

1. Forward, Forward
2. Forward, Backward
3. Backward, Forward
4. Backward, Backward

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. A $5\text{kg}$ block slides down an inclined plane, having angle of inclination ${30}^{\circ }$ from horizontal. Find the acceleration (${\text{m/s}}^2$) of block, if the coefficient of kinetic friction is ${\mu }_k=\frac{1}{2\sqrt{3}}$. Take $g=10{\text{m/s}}^2$ .

1. $2.5{\text{m/s}}^2$
2. $3.5{\text{m/s}}^2$
3. $10{\text{m/s}}^2$
4. $7.5{\text{m/s}}^2$

Q.

A 1.0 kg block collides with a horizontal light spring of force constant 2 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 m/s
2. $\sqrt{52}m/s$
3. 25 m/s
4. none of these

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/$s^2$

2. 2.1 m/$s^2$

3. 1 m/$s^2$

4. 2 m/$s^2$

Q. A $5\text{kg}$ block is pushed along a floor by a constant applied force that is horizontal and has a magnitude of $60\text{N}$. The figure given below is the block's speed $v$ versus time $t$ as the block moves along $x$ - axis on the floor. What is the coefficient of kinetic friction between the block and the floor? [Take $g=10{\text{m/s}}^2$]

1. $0.1$
2. $0.3$
3. $0.45$
4. $0.6$

Q. Block A is pressed against the wall by Force F, F=60 N, find friction force between block & wall. (${\mu }_s=0.8,{\mu }_k=0.7$)

1. 48 N
2. 42 N
3. 40 N
4. 36 N

Q. From the given figure, velocity of block at t=10 sec is
(g = 10 m/$s^2$)

1. 0 m/s
2. 6 m/s
3. 8 m/s
4. 12 m/s

Q. Two blocks of masses $4kg$ and $10kg$ are connected by a flexible inextensible string as shown in given figure. The pulley is assumed to be light and frictionless. The coefficient of friction between the $4kg$ block and the suface is $0.2$ (${\mu }_s={\mu }_k=0.2$). The angle of inclination of the plane is ${30}^{\circ }$. Assuming the sytem to be released from rest, the acceleration of $10kg$ block is $(g=10m{s}^{-2})$

1. $5.2m{s}^{-2}$
2. $6.6m{s}^{-2}$
3. $41.8m{s}^{-2}$
4. $13m{s}^{-2}$

Q. For two bodies to collide, they

1. must come in physical contact with each other.
2. must not come in physical contact with each other.
3. may or may not come in physical contact with each other.
4. none of these.

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/$s^2$

2. 2.1 m/$s^2$

3. 1 m/$s^2$

4. 2 m/$s^2$

Q. A $5\text{kg}$ block is pushed along a floor by a constant applied force that is horizontal and has a magnitude of $60\text{N}$. The figure given below is the block's speed $v$ versus time $t$ as the block moves along $x$ - axis on the floor. What is the coefficient of kinetic friction between the block and the floor? [Take $g=10{\text{m/s}}^2$]

1. $0.1$
2. $0.3$
3. $0.45$
4. $0.6$

Q. The direction of Kinetic friction at the given instant
1) On the block, exerted by the ground
2) On the ground, exerted by the block

1. Forward, Forward
2. Forward, Backward
3. Backward, Forward
4. Backward, Backward

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. Block A is resting on floor and then it is pulled by a force F=2t (t= time), find time when block starts to slip on floor (take ${\mu }_s=\frac{1}{\sqrt{2}}$ ).

1. 8 sec
2. 12 sec
3. 20 sec
4. 15 sec

Q. Coefficient of kinetic friction between $3\text{kg}\text{and}2\text{kg}$ block is $0.25$. The horizontal table surface is smooth. Find the acceleration $($in ${\text{m/s}}^2)$ of block of mass $10\text{kg}$.