Block on a Block Problems

Q.

Two blocks are pushed against a wall and held at equilibrium. If all surfaces have friction, then what is the direction of friction from the wall on block B

1. Upwards

2. Downwards

Q. For the given situation, choose the correct option.

1. At $t=15\text{s}$, the acceleration of $\text{2 kg}$ block is ${\text{11 ms}}^{-2}$.
2. At $t=1\text{s}$, the force of friction between $\text{2 kg}$ and $\text{4 kg}$ blocks is $\text{2 N}$.
3. At $t=4\text{s}$, the force of friction between the ground and $\text{4 kg}$ block is $\text{18 N}$.
4. At $t=1\text{s}$, the force of friction between $\text{2 kg}$ and $\text{4 kg}$ blocks is zero.

Q.

Two blocks $m_1$and $m_2$, are acted upon by the forces $F_1$ and $F_2$ as shown in the fig. If there is no relative sliding between the blocks and the ground is smooth, find the magnitude of static friction between the blocks.Make necessary assumptions.

1. 

2. 

3. 

4. 

Q.

In the adjoining figure, the coefficient of friction between wedge (of mass M) and block (of mass m) is $\mu$.

Find the minimum horizontal force F required to keep the block stationary with respect to wedge.

1. 
2. 
3. 
4. 

Q.

Block A is kept on top of block B and moves leftwards with respect to B. Assume the friction to be present between the blocks. The direction of friction force on A by B, will be?

1. ↙

2. ↘

3. →

4. ←

Q.

Two blocks of masses M = 5 kg and m = 3 kg are placed on a horizontal surface as shown in the figure. The coefficient of friction between the blocks is 0.5 and that between the block M and the horizontal surface is 0.7. What is the maximum horizontal force F that can be applied to block M so that both the blocks move together?

1. 4 N

2. 16 N

3. 24 N

4. 96 N

Q. Two blocks are held against a wall at equilibrium. If all surfaces have friction, then the direction of friction from the wall on block B .

1. acts upwards
2. acts downwards
3. does not act

Q. If block A is kept on block B and moves in the positive direction with respect to B, then in which direction will the frictional force on A by B act?

1. Negative
2. Positive

Q. Two blocks are held against a frictionless wall and released. If mass of A is less than the mass of B, then the friction between A and B.

1. acts downwards
2. acts upwards
3. does not act

Q. A $40\text{kg}$ slab rests on a frictionless floor. A $10\text{kg}$ block rests on top of the slab. The static coefficient of friction between the block and the slab is 0.60 while the kinetic coefficient of friction is 0.40. The $10\text{kg}$ block is acted upon by a horizontal force of $100\text{N}$ . The resulting acceleration of the slab will be

1. $1.5{\text{ms}}^{-2}$
2. $2.0{\text{ms}}^{-2}$
3. $10{\text{ms}}^{-2}$
4. $1.0{\text{ms}}^{-2}$