Laws of Motion

A heavy box of mass 50 kg is moving on a horizontal surface. If co-efficient of kinetic friction between the box and horizontal surface is 0.3 then force of kinetic friction is :

1. 1470 N
2. 147 N
3. 1.47 N
4. 14.7 N

A wooden block, initially at rest on the ground, is pushed by a force which increases linearly with time t. Which of the following curve best describes acceleration of the block with time :

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A 2 kg brick begins to slide over a surface which is inclined at an angle of 45 with respect to horizontal axis. The co-efficient of static friction between their surfaces is:

1. 1
2. 1.7
3. 0.5
4. 1 3

Consider a block and trolley system as shown in figure. If the coefficient of kinetic friction between the trolley and the surface is 0.04, the acceleration of the system in ms-2 is : (Consider that the string is massless and unstretchable and the pulley is also massless and frictionless) : [figure]

1. 1.2
2. 4
3. 3
4. 2

A ball of mass 0.5 kg is attached to a string of length 50 cm. The ball is rotated on a horizontal circular path about its vertical axis. The maximum tension that the string can bear is 400 N. The maximum possible value of angular velocity of the ball in rad/s is :

1. 1600
2. 20
3. 40
4. 1000

A body of mass 4 kg experiences two forces F1=5 i+8 j+7 k and F2=3 i-4 j-3 k. The acceleration acting on the body is :

1. 2 i+ j+ k
2. 4 i+2 j+2 k
3. -2 i- j- k
4. 2 i+3 j+3 k

A cricket player catches a ball of mass 120 g moving with 25 m/s speed. If the catching process is completed in 0.1 s then the magnitude of force exerted by the ball on the hand of player will be (in SI unit) :

1. 30
2. 24
3. 12
4. 25

In the given arrangement of a doubly inclined plane two blocks of masses M and m are placed. The blocks are connected by a light string passing over an ideal pulley as shown. The coefficient of friction between the surface of the plane and the blocks is 0.25. The value of m, for which M=10 kg will move down with an acceleration of 2 m/s2, is: (take g=10 m/s2 and 37 =3/4) [figure]

1. 4.5 kg
2. 6.5 kg
3. 9 kg
4. 2.25 kg

An artillery piece of mass M1 fires a shell of mass M2 horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is:

1. M1/(M1+M2)
2. M2M1
3. M1M2
4. M2/(M1+M2)

A coin is placed on a disc. The coefficient of friction between the coin and the disc is . If the distance of the coin from the center of the disc is r, the maximum angular velocity which can be given to the disc, so that the coin does not slip away, is :

1. r g
2. gr
3. gr
4. rg