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A block of mass 2 kg is at rest on a floor. The coefficient of static friction between block and the floor is 0.54. A horizontal force of 2.8 N is applied to the block. What should be the frictional force between the block and the floor? (take, g =10 m/s²)

1) 8.8 N 2) 5.8 N 3) 2.8 N 4) 10.8 N Answer: 3) 2.8 N Solution: mass of block = 2kg coefficient of static friction = 0.4 Force... View Article

10000 small balls, each weighing lg, strike one square centimetre of area per second with a velocity 100 ms^-1 in a normal direction and rebound with the same velocity. The value of pressure on the surface will be

1) 2 × 103 Nm-2 2) 2 × 105 Nm-2 3) 107 Nm-2 4) 2 × 107 Nm-2 Answer: 4) 2 × 107 Nm-2 Solution: Pressure =... View Article

Two masses of M and 4M are moving with equal kinetic energy. The ratio of their linear momenta is

1) 1 : 8 2) 1 : 4 3) 1 : 2 4) 4 : 1 Answer: 3) 1 : 2 Solution: Relation between linear momentum and kinetic energy p... View Article

A bullet of mass 10 g moving with 300 m/s hits a block of ice of mass 5 kg and drops dead. The velocity of ice is

1) 50 cm/s 2) 60 cm/s 3) 40 cm/s 4) 200 cm/s Answer: 2) 60 cm/s Solution: Applying law of conservation of linear momentum... View Article

A rocket of mass 100 kg burns 0.1 kg of fuel per second. If velocity of exhaust gas is 1 kms^-1 , then it lifts with an acceleration of

1) 1000 ms-2 2) 100 ms-2 3) 10 ms-2 4) 1 ms-2 Answer: 4) 1 ms-2 Solution: Mass (m) = 100 Kg Velocity= 1 km/sec = 1000 m/s dm/dt = 0.1 Thrust... View Article

A hockey player receives a corner shot at a speed of 15 ms^-1 at an angle of 30° with the y – axis and then shoots the ball of mass 100 g along the negative x-axis with a speed of 30 ms^-1. If it remains in contact with the hockey stick for 0.01s, the force imparted to the ball in the x-direction is

1) 281.25 N 2) 187.5 N 3) 562.5 N 4) 375 N Answer: Mass of the ball, m = 100 g = 0.1 Kg Initial velocity of the ball, u = 30 m/s Final... View Article

A shell of mass 10 kg is moving with a velocity of 10 ms^-1 when it blasts and forms two parts of mass 9 kg and 1 kg respectively. If the 1st mass is stationary, the velocity of the 2nd is

1) 1 ms-1 2) 10 ms-1 3) 100 ms-1 4) 1000 ms-1 Answer:3) 100 ms-1 Solution: From the conservation of momentum m1v1 = m2v2 + m3v3 10 x 10 =... View Article

A cricket ball of mass 0.25 kg with a speed of 10 m/s collides with a bat and returns with the same speed within 0.01s. The force acted on the bat is

1) 25 N 2) 50 N 3) 250 N 4) 500 N Answer: 4) 500 N Solution: Δp = 2mv = 2 x 0.25 x 10 = 5 kgm/s F = Δp/Δt = 5/0.01 = 500 N... View Article

A stationary bomb explodes into three pieces. One piece of 2 kg mass moves with a velocity of 8ms^-1 at right angles to the other piece of mass 1 kg moving with a velocity of 12 ms^-1. If the mass of the third piece is 0.5 kg, then its velocity is

1) 10 ms-1 2) 20 ms-1 3) 30 ms-1 4) 40 ms-1 5) 50 ms-1 Answer: 4) 40 ms-1 Solution: Initial momentum is zero since the ball is... View Article

A shell of mass 200 g is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 m/s, calculate the recoil speed of the gun

1) 16 cm/s 2) 8 m/s 3) 4 m/s 4) 16 m/s Answer: 1) 16 cm/s Solution: Given Mass of the shell = 200 g = 200 x 10-3 kg Mass of the gun,... View Article

A lift is moving down with acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively

1) g, g 2) g – a, g – a 3) g – a, g 4) a, g Answer: 3) g – a, g Solution: For a man standing in the lift, the... View Article

A force of 1200 N acts on a 0.5 kg steel ball as a result of a collision lasting 25 ms. If the force is in a direction opposite to the initial velocity of 14 ms^-1, then the final speed of the steel ball would be

1) 24 ms-1 2) 35 ms-1 3) 12 ms-1 4) 46 ms-1 Answer: 4) 46 ms-1 Solution: For an impulsive force of 1200 N F = Δp/Δt F... View Article

An 80 kg person is parachuting and is experiencing a downward acceleration of 2.8 ms^-2. The mass of the parachute is 5 kg. The upward force on the open parachute is (take, g = 9.8 ms^-2)

1) 595 N 2) 675 N 3) 456 N 4) 925 N Answer: 1) 595 N Solution: m = (80 kg + 5 Kg) = 85 kg mg - F = ma 85 x 9.8 - F = 85 x 2.8 F... View Article

Which of the following quantities measured from different inertial reference frames are the same?

1) Force 2) Velocity 3) Displacement 4) Kinetic energy Answer: 1) Force and 4) Kinetic energy Solution: Force and kinetic... View Article

A student unable to answer a question on Newton’s laws of motion attempts to pull himself up by tugging on his hair. He will not succeed

1) as the force exerted is small 2) the frictional force while gripping, is small 3) Newton's law of inertia is not applicable to living beings... View Article

A man slides down on a telegraphic pole with an acceleration equal to one-fourth of acceleration due to gravity. The frictional force between man and pole is equal to in terms of man’s weight w

1) W/4 2) W/2 3) 3W/4 4) W Answer: 3) 3W/4 Solution: Given a = g/4 ma = W - f Frictional force f = W - ma W is the weight of the... View Article