Laws of Motion · Question 8

A bob is whirled in a horizontal circle by means of a string at an initial speed of 10 rpm. If the tension in the string is quadrupled while keeping the radius constant, the new speed is:

1. 20 rpm
2. 40 rpm
3. 5 rpm
4. 10 rpm

A box of mass 5 kg is pulled by a cord, up along a frictionless plane inclined at 30 with the horizontal. The tension in the cord is 30 N. The acceleration of the box is (Take g = 10 m s-2)

1. 2 m s-2
2. Zero
3. 0.1 m s-2
4. 1 m s-2

A football player is moving southward and suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is :

1. along northward
2. along north-east
3. along south-west
4. along eastward

Calculate the maximum acceleration of a moving car so that a body lying on the floor of the car remains stationary. The coefficient of static friction between the body and the floor is 0.15 (g = 10 m s-2 ).

1. 150 m s-2
2. 1.5 m s-2
3. 50 m s-2
4. 1.2 m s-2

A shell of mass m is at rest initially. It explodes into three fragments having mass in the ratio 2 : 2 : 1. If the fragments having equal mass fly off along mutually perpendicular directions with speed v, the speed of the third (lighter) fragment is :

1. v
2. 2v
3. 2 2v
4. 3 2v

The distance covered by a body of mass 5 g having linear momentum 0.3 kg m/s in 5 s is :

1. 0.3 m
2. 300 m
3. 30 m
4. 3 m

In the diagram shown, the normal reaction force between 2 kg and 1 kg is (Consider the surface, to be smooth) : (Given g = 10 m s-2) [figure]

1. 10 N
2. 25 N
3. 39 N
4. 6 N

A ball of mass 0.15 kg is dropped from a height 10 m, strikes the ground and rebounds to the same height. The magnitude of impulse imparted to the ball is (g = 10 m/s2) nearly :

1. 1.4 kg m/s
2. 0 kg m/s
3. 4.2 kg m/s
4. 2.1 kg m/s

Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity (g) is : [figure]

1. g/2
2. g/5
3. g/10
4. g

A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be : (g = 10 m/s2)

1. 102 rad/s
2. 10 rad/s
3. 10 rad/s
4. 10 rad/s