Laws of Motion · Question 53

A block B is pushed momentarily along a horizontal surface with an initial velocity V. If μ is the coefficient of sliding friction between B and the surface, block B will come to rest after a time [figure]

1. g /V
2. g/V
3. V/g
4. V/(g )

A 0.5 kg ball moving with a speed of 12 m/s strikes a hard wall at an angle of 30 with the wall. It is reflected with the same speed at the same angle. If the ball is in contact with the wall for 0.25 seconds, the average force acting on the wall is :

1. 96 N
2. 48 N
3. 24 N
4. 12 N

A tube of length L is filled completely with an incompressible liquid of mass M and closed at both the ends. The tube is then rotated in a horizontal plane about one of its ends with a uniform angular velocity . The force exerted by the liquid at the other end is

1. ML2 22
2. ML 22
3. ML2 2
4. ML 2

A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18 kg mass is 6 m s-1. The kinetic energy of the other mass is :

1. 324 J
2. 486 J
3. 256 J
4. 524 J

A block of mass m is placed on a smooth wedge of inclination . The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block will be (g is acceleration due to gravity)

1. mg
2. mg
3. mg
4. mg/

The coefficient of static friction, s, between block A of mass 2 kg and the table as shown in the figure is 0.2. What would be the maximum mass value of block B so that the two blocks do not move? The string and the pulley are assumed to be smooth and massless. (g = 10 m/s2) [figure]

1. 2.0 kg
2. 4.0 kg
3. 0.2 kg
4. 0.4 kg

A man weighs 80 kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of 5 m/s2. What would be the reading on the scale ? (g = 10 m/s2)

1. zero
2. 400 N
3. 800 N
4. 1200 N

A monkey of mass 20 kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope ? (g = 10 m/s2)

1. 5 m/s2
2. 10 m/s2
3. 25 m/s2
4. 2.5 m/s2

A stationary particle explodes into two particles of masses m1 and m2 which move in opposite directions with velocities v1 and v2. The ratio of their kinetic energies E1/E2 is :

1. m2/m1
2. m1/m2
3. 1
4. m1v2/m2v1

An object of mass 3 kg is at rest. Now a force of F = 6t2 i + 4t j is applied on the object then velocity of object at t = 3 sec. is

1. 18 i + 3 j
2. 18 i + 6 j
3. 3 i + 18 j
4. 18 i + 4 j