Laws of Motion · Question 35

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 car is moving in a circular horizontal track of radius 10 m with a constant speed of 10 m/s. A bob is suspended from the roof of the car by a light wire of length 1.0 m. The angle made by the wire with the vertical is

1. 3
2. 6
3. 4
4. 0

A person holding a rifle (mass of person and rifle together is 100 kg) stands on a smooth surface and fires 10 shots horizontally, in 5 s. Each bullet has a mass of 10 g with a muzzle velocity of 800 m s-1. The final velocity acquired by the person and the average force exerted on the person are :

1. -0.08 m s-1, 16 N
2. -0.8 m s-1, 16 N
3. -1.6 m s-1, 16 N
4. -1.6 m s-1, 8 N

A car of mass m is moving on a level circular track of radius R. If s represents the coefficient of static friction between the road and tyres of the car, the maximum speed of the car in circular motion is given by

1. s mRg
2. Rg s
3. mRg s
4. s Rg

A car of mass 1000 kg negotiates a banked curve of radius 90 m on a frictionless road. If the banking angle is 45 , the speed of the car is

1. 20 m s-1
2. 30 m s-1
3. 5 m s-1
4. 10 m s-1

A conveyor belt is moving at a constant speed of 2 m s-1. A box is gently dropped on it. The coefficient of friction between them is = 0.5. The distance that the box will move relative to belt before coming to rest on it, taking g = 10 m s-2, is

1. 0.4 m
2. 1.2 m
3. 0.6 m
4. zero

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

A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is

1. MV
2. 1.5 MV
3. 2MV
4. zero

A block of mass m is in contact with the cart C as shown in the figure. The coefficient of static friction between the block and the cart is . The acceleration of the cart that will prevent the block from falling satisfies [figure]

1. > mg
2. > g m
3. g
4. < g

A gramophone record is revolving with an angular velocity . A coin is placed at a distance r from the centre of the record. The static coefficient of friction is . The coin will revolve with the record if

1. r = 2
2. r < 2
3. r 2
4. r 2