Friction General Understanding

Q.

What is $v=u+at$?

Q.

A block A kept on an inclined surface just begins to slide if the inclination is ${30}^{\circ }$. The block is replaced by another block B and it is found that it just begins to slide if the inclination is ${40}^{\circ }$.

1. mass of A = mass of B

2. mass of A > mass of B

3. mass of A < mass of B

4. all the three are possible

Q.

A force of 20 N is applied on a body of mass 4 kg kept on a rough surface having coefficient of friction 0.1. Find acceleration of body. Take g = 10 m/s²

1. 7 m/s²

2. 4 m/s²

3. 9 m/s²

4. 6 m/s²

Q. A 250 g block slides on a rough horizontal table. Find the work done by the frictional force in bringing the block to rest if it is initially moving at a speed of 40 cm/s. If the friction coefficient between the table and the block is 0.1, how far does the block move before coming to rest ?

Q. A wooden block which is being acted upon by forces $F_1=10\text{N},F_2=2\text{N}$ is at rest on a rough horizontal plane as shown in figure. If force $F_1$ is removed, the resultant force acting on the block will be

1. $2\text{N}$ towards left
2. $2\text{N}$ towards right
3. Zero
4. Cannot be determined.

Q. Find the direction of friction on the block for the figure shown.

1. $\text{Perpendicular to the plane}$
2. $\text{Up the plane}$
3. $\text{Down the plane}$
4. $\text{None of these}$

Q. Do we consider normal reaction as a conservative force or non conservative for

Q. A $3\text{kg}$ block is resting on rough horizontal surface of a truck moving with acceleration of $2{\text{m/s}}^2$ on a horizontal road. The force of friction on the block is

1. Zero
2. $6$ N
3. $4$ N
4. $8$ N

Q.

In the figure shown co-efficient of friction between the block B and the block C is 0.4. there is no friction between the block C and the surface on which it is placed. The system of blocks is released from rest in the situation shown in the diagram. Find the distance moved by the block C when block A descends through a distance 2 m. Given masses of the blocks are $m_A$ = 3 kg, $m_B$ = 5 kg and $m_C$ = 10 kg.

1. 0 m

2. 5 m

3. 4 m

4. 2 m

Q. A billiards player hits a stationary ball by an identicaI ball to pocket the target ball in a comer pocket that is at an angle of 35with respect to the direction of motion of the first ball. Assuming the collision as elastic and that frictionaI and rotational motions are not important, the angle made by the target ball with respect to the incoming ball is

Q. For the figure shown below, choose the correct option(s) (Assume all surfaces are rough and all velocities are with respect to ground).

1. Friction force on block E and B is rightward.
2. Friction force on block E and B is leftward.
3. Friction force on block A and D is leftwards.
4. Friction force on block A and D is rightwards.

Q. A block of mass M moving with speed u collides elastically with block B of mass m which is connected to block C of mass m with a spring. When the compression in spring is maximum, the velocity of block C with respect to block A is. Neglect friction.(why CANT WE SOLVE IT LIKE Mu=2mv where v is common velocity of BLOCK B And C)

Q. A force of 10 N is applied on the right block of a system of two blocks of 1 kg mass each, on a rough horizontal plane. Coefficient of friction is  = 0.2 for both blocks. The spring is initially in relaxed state. Acceleration of centre of mass at initial ins†an t will be (g = 10 m/s2)

Q. A BLOCK OF Mass 5 kg is kept above another block of mass 10 kg 5 kg block is moving with the acceleration of 2 m/s2 which is less 10 kg mass block find frictional force applied by 10 kg block 1)50N 2)20N 3)10N 4)NOT

Q. 54. What is the need for banking of road??

Q. A block is shot with an initial velocity of $5m/s$ on a rough horizontal plane. Find the distance covered by the block till it comes to rest. Given coefficient of friction between the surfaces of contact is $0.1\text{and}g=10m/s^2$.

1. $5m$
2. $10m$
3. $12.5m$
4. $25m$

Q.

Define coefficient of rolling friction ?

Q. A mass m attached to an ideal spring is released from natural length position of spring whose other end is connected to a block of mass M placed on rough surface of friction coefficient μ. Find μ for which the block of mass M does not slip 1 ) μ>2m/M 2) μ≤2m/M 3) μ≥ m/M 4)μ≤ m/M

Q. In the figure, block $m_1$ is loaded on block $m_2$. If there is no relative sliding between the blocks and the inclined plane is smooth, the frictional force acting between the blocks is:

1. $\mu m_2\sin \theta$
2. $\mu m_1\cos \theta$
3. $\mu m_1\sin \theta$
4. Zero

Q. A block is shot with an initial velocity of $5m/s$ on a rough horizontal plane. Find the distance covered by the block till it comes to rest. Given coefficient of friction between the surfaces of contact is $0.1\text{and}g=10m/s^2$.

1. $5m$
2. $10m$
3. $12.5m$
4. $25m$

Q. In the figure shown, find the direction of friction on $A$ and $B$ respectively on the surface, which is in contact with the surface of block $A$.

1. $\text{Forward, Backward}$
2. $\text{Backward, Backward}$
3. $\text{Backward, Forward}$
4. $\text{Forward, Forward}$

Q. is it necessary that body with uniform mass should have same material composition that is can the centre of mass lie at the centre of object with the uniform mass distribution but with the composition of different material

Q. what is the minimum possible value of coefficient of friction

Q. A block is placed on a horizontal table and a string is connected as shown. A force F is applied on the block, but the tension in the string is 0. This means the friction on the block is .

1. equal to F
2. more than F
3. less than F
4. zero

Q. Friction also depends on smoothness of the surface, even if materials are same

1. False
2. True

Q.

There is a box of 70 kg on a rough surface and Ram is just able to pull the box by applying a force of $F_1$ (Figure1) Avinash tries to pull the same box but in different orientation (figure (ii)). He had to apply force $F_2$ is order to just move the box. Who had to apply a lesser force in order to just move the box?

1. (a)Both applied same force

2. Ram

3. Avinash

4. (a)Can't say until coefficient of friction is given.

Q. Which of the following statements is correct about frictional force?

1. It always acts perpendicular to the surface.
2. It may act perpendicular to the surface.
3. It may act at some angle to the surface.
4. It always acts parallel to the surface.

Q. 53) A metallic chain 1 m long lies on a horizontal surface of a table. The chain starts sliding on the table if 25 cm (or more of it) hangs over the edge of a table. The correct value of the coefficient of friction between the table and the chain is.
$$\begin{gathered} \left(1\right)\frac{1}{3} \\ \left(2\right)\frac{2}{3} \\ \left(3\right)\frac{1}{4} \\ \left(5\right)\frac{1}{5} \end{gathered}$$

Q.

It is easier to make a body roll over a surface rather than to slide. Why?

Q. A mosquito is sitting on an L.P. record disc rotating on a turn table at $33\frac{1}{3}$ revolutions per minute. The distance of the mosquito from the centre of the turn table is 10 cm. Show that the friction coefficient between the record and the mosquito is greater than π²/81.