A spring of force constant 800 Nm-1 has an extension of 5cm. The work done in extending it from 5 cm to 15 cm is 1) 16 J 2) 8 J 3) 32 J 4) 24 J Answer: 2) 8 J Solution: Force constant, k = 800 N/m Work done in extending from 5 cm to 15 cm... View Article
A bullet of mass 10 g is fired horizontally with a velocity 1000 ms-1 from a rifle situated at a height 50 m above the ground. If the bullet reaches the ground with a velocity 500 ms-1, the work done against air resistance in the trajectory of the bullet is (take g = 10 m-2) 1) 5005 J 2) 3755 J 3) 3750 J 4) 17.5 J Answer: 2) 3755 J Solution: Work done against the air resistance is the energy lost W = (mgh... View Article
A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time, the particle goes up is 1) –0.5 J 2) –1.25 J 3) 1.25 J 4) 0.5 J Answer: 2) –1.25 J Solution: Mass = 100 g Speed, u = 5 m/s Work done by... View Article
A body moves a distance of 10 m along a straight line under action of 5 N force. If work done is 25 J, then the angle between the force and direction of motion of the body will be 1) 75° 2) 60° 3) 45° 4) 30° Answer: 2) 60° Solution: Distance, S = 10 m Force, F = 5 N Work done, W = 25 J W =... View Article
When a force is applied to a moving body, its motion is retarded. Then, the work done is 1) positive 2) negative 3) zero 4) positive and negative Answer: 2) negative Solution: Work is said to be done on that body when a... View Article
Force of 50 N acting on a body at an angle θ with horizontal. If 150 J work is done by displacing it 3 m, then θ is 1) 60° 2) 30° 3) 0° 4) 45° Answer: 3) 0° Solution: The horizontal component of force = Fcos θ Work done =... View Article
A spring stores 1 J of energy for compression of 1 mm. The additional work to be done to compress it further by 1 mm is 1) 1 J 2) 2 J 3) 3 J 4) 4 J 5) 0.5 J Answer: 3) 3 J Solution: W1 = (1/2)kx2 = (1/2)k(1 x 10-3)2 k = 2 x 106 W2 = (1/2)(2 x... View Article
A ball is dropped from a height of 20 m. If the coefficient of restitution is 0.9, what will be the height attained after the first bounce? 1) 1.62 m 2) 16.2 m 3) 18 m 4) 14 m Answer: 2) 16.2 m Solution: Ball is dropped from a height, h= 20 m coefficient of restitution =... View Article
For inelastic collision between two spherical rigid bodies 1) the total kinetic energy is conserved 2) the total mechanical energy is not conserved 3) the linear momentum is not conserved 4) the linear... View Article
If the heart pushes 1 cc of blood in 1 s under pressure 20000 Nm-2, the power of the heart is 1) 0.02 W 2) 400 W 3) 5 × 10-10 W 4) 0.2 W Answer: 1) 0.02 W Solution: Given, Pressure, P = 20000 Nm-2 Volume per second... View Article
