JEE Main: Laws Of Motion Set 1 Quiz! Physics

1. A block of mass M is suspended on the side 'A' of a pulley with a string. A monkey of mass 2M is climbing on the side B with a uniform acceleration of g/4 (with respect to rope). If there is no friction between pulley and string and between string and monkey then what will be the tension in the string?

13/18 Mg

3/2 Mg

4 Mg

5/2 Mg

Explanation

2. A car of mass 1500 kg collides with another car (In the state of rest) of mass 1350 kg due to which the second car starts moving with an acceleration of 4

straight m divided by straight s squared

. What will be the acceleration of the first car?

4.8 m/s2

7.75 m/s2

5.2

3.6

Explanation

3. A block of mass 15 kg is suspended by three strings as shown in the figure. Choose the correct option on the basis of the diagram. (Take g = 10 m/s²)

TA = 400N, TB = 500N

TA = 200N, TB = 250N

TA = 302.5N, TB = 225N

TA = 225N, TB = 112.5N

From the diagram it is clear that there are three forces acting in the same point. We can apply Lami’s Theorem

$straight T subscript straight C equals 150 space N comma space then space on space solving space the space equation space we space will space get<br /> straight T subscript straight A equals 200 space N comma space T subscript B equals 2 subscript S 50 space N$

Explanation

From the diagram it is clear that there are three forces acting in the same point. We can apply Lami’s Theorem

$straight T subscript straight C equals 150 space N comma space then space on space solving space the space equation space we space will space get<br /> straight T subscript straight A equals 200 space N comma space T subscript B equals 2 subscript S 50 space N$

4.

Explanation

5. A lift is going up and the change in the speed of the lift is shown with the help of the diagram. If the total mass of the lift with passenger is 1600 kg then what will be the tension in the rope pulling the lift at time t = 9 seconds.

17700 N

15000 N

12000 N

12300 N

As per the diagram the speed of the lift is increasing in the first 2 seconds. From 2s to 8s, the speed of the lift is constant and for the last two seconds, the speed of the lift is decreasing. At the 9th second, there will be retardation. The tension in the rope will only be due to the weight of the lift and the person in the lift. The direction of the weight will be opposite to the direction of the tension in the rope.

Explanation

As per the diagram the speed of the lift is increasing in the first 2 seconds. From 2s to 8s, the speed of the lift is constant and for the last two seconds, the speed of the lift is decreasing. At the 9th second, there will be retardation. The tension in the rope will only be due to the weight of the lift and the person in the lift. The direction of the weight will be opposite to the direction of the tension in the rope.

6. A block of mass M₁ is attached to a string of mass M₂ and length L. If a horizontal force F is applied on the string to pull the block then what will be the tension at the midpoint of the string?

Explanation

7. A pendulum, with a bob of mass 'm', is hung from the ceiling of a car. The car is ascending on an inclined plane with an angle of inclination = 45⁰. If the car is moving with an acceleration a= g, then what will be the angle subtended by the string of the pendulum with the normal to the ceiling in equilibrium.

Let the angle in the state of equilibrium with the normal = α; then from the free body diagram of car;

Explanation

Let the angle in the state of equilibrium with the normal = α; then from the free body diagram of car;

8. In the arrangement shown in the figure, the block of mass 'm' is moving upward with acceleration 'a'. The tension in all the string is same. If whole system starts from rest then what will be the value of velocity 'v' after 2 seconds?

Explanation

9. Three forces F₁, F₂ and F₃ are acting on a block of mass 'M'. The box is in the state of equilibrium and force F₂ is perpendicular to the force F₃. Force F₁ is removed and due to it, the box starts moving with some acceleration. What should be the value of acceleration?

Explanation