chapter-5-LAWS OF MOTION

1. When a bus suddenly takes a turn, the passengers are thrown outwards because of

• inertia of direction

• acceleration of motion

• speed of motion

• both (b) and (c)

2. The velocity of a body of mass 20kg decreases from 20ms^-1 to 5ms^-1 in a distance of 100m. Force on the body is

• -27.5N

• -47.5N

• -37.5N

• -67.5N

3. A person is standing in an elevator. In which situation he finds his weight less than actual weight

• the elevator moves upward with constant acceleration

• the elevator moves downward with constant acceleration

• the elevator moves upward with uniform velocity

• the elevator moves downward with uniform velocity.

4.A force of 10N acts on a body of mass 20kg for 10s. Change in its momentum is

• 5kgms^-1

• 100kgms^-1

• 200kgms^-1

• 1000kgms^-1

5. A rocket with a lift-off mass 3.5 x 10⁴ kg is blasted upwards with an initial acceleration of 10ms^-2. Then the initial thrust of the blast is

• 1.75 x 10⁵ N

• 3.5 x 10 ⁵N

• 7 x 10⁵N

• 14 x 10⁵N

6. As shown in figure, the tension in the horizontal cord is 30N. The weight W and tension in the string OA in newton are

• $30\sqrt{3},30$
  

• $30\sqrt{3},60$

• $60\sqrt{3},30$

• none of these

7.Three blocks of masses 2kg, 3kg and 5kg are connected to each other with light string and are then placed on a frictionless surface as shown in figure. The system is pulled by a force F = 10N, then tension T₁ will be?

• 1N

• 5N

• 8N

• 10N

8.Two masses of 5kg and 10kg are connected to a pulley as shown. What will be the acceleration of the system?

• g

• g/2

• g/3

• g/4

9.A block of 1kg is stopped against a wall by applying a force F perpendicular to the wall. If µ = 0.2, then minimum value of F will be

• 980N

• 49N

• 98N

• 490N

10.Two bodies A and B of respective masses 5kg and 10kg in contact with each other rest on a table against a rigid partition, as shown. The coefficient of friction between the bodies and table is 0.15. A force F of 200N is applied horizontally at A. The reaction of the partition is

• 178N right

• 178N left

• 200N right

• 200N left