Net Contact Force

Q.

A body of mass 400g slides on a rough horizontal surface. If the frictional force is 3.0 N, find (a) the angle made by the contact force on the body with the vertical and (b) the magnitude of the contact force. Take g = 10$\frac{m}{s^2}$

1. 53⁰, 4N

2. 37⁰, 5N

3. 37⁰, 4N

4. None of these

Q.

A body of mass M is kept on a rough horizontal surface (friction coefficient = $\mu$). A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on the body is F, where

1. F = Mg

2. F = μMg

3. 

4. 

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

1. may increase or decrease

2. Increase

3. decrease

4. Remain the same

Q. The surface between A & B is rough & ${\mu }_k=0.4$, find frictional force on A.

1. 20 N, right
2. 20 N, left
3. 60 N, right
4. 60 N, left

Q. Find the direction of the reaction force on the block for the figure shown.

1. $\text{Perpendicular to the plane}$
2. $\text{At an angle to the plane}$
3. $\text{Up the plane}$
4. $\text{Down the plane}$

Q. A force is acting on a body of mass $3kg$ kept on a rough horizontal surface. If a friction force of $40N$ is required to keep the body at rest under the action of this external force. Find the contact force acting on the body. (Take $g=10m/s^2$)

1. $30N$
2. $40N$
3. $50N$
4. $100N$

Q. A scooter starting from rest moves with constant acceleration for time $\Delta t_1$ , then with a constant velocity for time $\Delta t_2$ and finally with constant deceleration for time $\Delta t_3$ to come to rest. A man of weight of $600\text{N}$ sitting behind the driver manages to be at rest with respect to the scooter without touching any other part. The force exerted by the seat on the man is

1. less than $600\text{N}$ throughout the journey.
2. more than $600\text{N}$ throughout the journey.
3. $600\text{N}$ throughout the journey.
4. $>600\text{N}$ for a times $\Delta t_1$ and $\Delta t_3$ and $=600\text{N}$ for $\Delta t_2$

Q. A body of mass $2kg$ is kept on a rough horizontal surface. If ${\mu }_s=0.5$, find the contact force between the body and the surface. Take $g=10m/s^2$.

1. $\text{Zero}$
2. $10N$
3. $10\sqrt{5}N$
4. $20N$

Q. Which of the following is correct when a person walks on a rough surface?

1. The normal reaction exerted by the surface keeps him moving
2. The force which the man exerts on the floor keeps him moving
3. The reaction of the force which the man exerts on floor keeps him moving
4. None of the above

Q. A body of mass $10kg$ lies on a rough inclined plane of inclination $\theta ={37}^{\circ }$ with the horizontal. When the force of $30N$ is applied on the block parallel to and upward the plane, the contact force by the plane on the block is nearby along

1. OB
2. OC
3. OD
4. OA