Laws of Motion

A ball of mass 0.5 kg moving with a velocity of 2 ms^-1 strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and wall is 10^-3 s, the average force exerted by the wall on the ball is

• 1125 N

• 1000 N

• 500 N

• 2000 N

Which of the following sets of concurrent forces may be in equilibrium ?

• F₁ = 3 N, F₂ = 5 N, F₃ = 1 N

• F₁ = 3 N, F₂ = 5 N, F₃ = 9 N

• F₁ = 3 N, F₂ = 5 N, F₃ = 6 N

• F₁ = 3 N, F₂ = 2 N, F₃ = 15 N

Two equal forces (P each) act at a point inclined to each other at an angle of120°. The magnitude of their resultant is

• P/2

• P/4

• P

• 2P

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

• as the force exerted is small

• the frictional force while gripping, is small

• Newton's law of inertia is not applicable to living beings

• as the force applied is internal to the system

Three long, straight parallel wires, carrying current, are arranged as shown in figure. The force experienced by a 25 cm length of wire C is

• 5.2 × 10³ N

• 2.5 × 10^-3 N

• zero

• 1.5 × 10^-3 N

The adjacent figure is the part of a horizontally stretched net. Section AB is stretched with a force of 10 N. The tensions in the sections BC and BF are

• 10 N, 11 N

• 10 N, 6 N

• 10 N, 10 N

• can't be calculated due to insufficient data

A body of mass 4 kg is accelerated upon by a constant force, travels a distance of 5 m in the first second and a distance of 2 m in the third second. The force acting on the body is

• 2 N

• 4 N

• 6 N

• 8 N

A body of mass 0.05 kg is observed to fall with an acceleration of 9.5 ms^-2. The opposing force of air on the body is (g = 9.8 ms^-2)

• 0.015 N

• 0.15 N

• 0.030 N

• zero

Three concurrent co-planar forces 1 N, 2 N and 3 N acting along different directions on a body

• can keep the body in equilibrium if 2 N and 3 N act at right angle

• can keep the body in equilibrium if 1 N and 2 N act at right angle

• cannot keep the body in equilibrium

• can keep the body in equilibrium in 1 N and 3 N act at an acute angle

Two rectangular blocks A and B of masses 2 kg and 3 kg respectively are connected by a spring of spring constant 10.8 Nm^-1 and are placed on a frictionless horizontal surface. The block A was given an initial velocity of 0.15 ms^-1. in the direction shown in the figure. The maximum compression of the spring during the motion is

• 0.01 m

• 0.02 m

• 0.05 m

• 0.03 m