Laws of Motion

A horizontal force 10 N is applied to a block A as shown in figure. The mass of blocks A and B are 2 kg and 3 kg respectively. The blocks slide over a frictionless surface. The force exerted by block A on block B is : [figure]

1. Zero
2. 4 N
3. 6 N
4. 10 N

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

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

Two blocks A and B of masses 3m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively [figure]

1. g3, g
2. g, g
3. g3, g3
4. g, g3

A block A of mass m1 rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass m2 is suspended. The coefficient of kinetic friction between the block and the table is k. When the block A is sliding on the table, the tension in the string is

1. m1m2(1+ k)g(m1+m2)
2. m1m2(1- k)g(m1+m2)
3. (m2+ km1)g(m1+m2)
4. (m2- km1)g(m1+m2)

Three blocks A, B and C, of masses 4 kg, 2 kg and 1 kg respectively, are in contact on a frictionless surface, as shown. If a force of 14 N is applied on the 4 kg block, then the contact force between A and B is [figure]

1. 8 N
2. 18 N
3. 2 N
4. 6 N

A system consists of three masses m1, m2 and m3 connected by a string passing over a pulley P. The mass m1 hangs freely and m2 and m3 are on a rough horizontal table (the coefficient of friction = ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m1 is (Assume m1 = m2 = m3 = m) [figure]

1. g(1 - g )9
2. 2g 3
3. g(1 - 2 )3
4. g(1 - 2 )2

Three blocks with masses m, 2m and 3m are connected by strings, as shown in the figure. After an upward force F is applied on block m, the masses move upwards at constant speed v. What is the net force on the block of mass 2m ? (g is the acceleration due to gravity) [figure]

1. 3mg
2. 6mg
3. zero
4. 2mg

A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1.0 m/s2. If g = 10 m s-2, the tension in the supporting cable is

1. 8600 N
2. 9680 N
3. 11000 N
4. 1200 N

The mass of a lift is 2000 kg. When the tension in the supporting cable is 28000 N, then its acceleration is:

1. 4 m s-2 upwards
2. 4 m s-2 downwards
3. 14 m s-2 upwards
4. 30 m s-2 downwards

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/

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 lift of mass 1000 kg which is moving with acceleration of 1 m/s2 in upward direction, then the tension developed in string which is connected to lift is

1. 9800 N
2. 10,800 N
3. 11,000 N
4. 10,000 N

Two masses as shown in the figure are suspended from a massless pulley. The acceleration of the system when masses are left free is [figure]

1. 2g3
2. g3
3. g9
4. g7