#### Work, Energy and Power Model Question Paper

11th Standard

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. A ball of mass 1 kg and another of mass 2kg are dropped from a tall building whose height is 80 m. After, a fall of 40 m each towards Earth, their respective kinetic energies will be in the ratio of

(a)

$\sqrt2:1$

(b)

$1:\sqrt2$

(c)

2:1

(d)

1:2

2. The coefficient of restitution e for a perfectly elastic collision is

(a)

1

(b)

0

(c)

$\alpha$

(d)

-1

3. What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop?

(a)

$\sqrt{2gR}$

(b)

$\sqrt{3gR}$

(c)

$\sqrt{5gR}$

(d)

$\sqrt{gR}$

4. A particle which is constrained to move along x-axis, is subjected to a force in the same direction which varies with the distance x of the particle from the origin as F(x) =kx + ax3. Here, k and a are positive constants. For x≥0, the functional form of the potential, energy U(x) of the particles

(a)

(b)

(c)

(d)

5. A cricket ball falls from a height of 40 m. What is the velocity with which the ball hits the ground?

(a)

40 m/s

(b)

20 m/s

(c)

16 m/s

(d)

28 m/s

6. 5 x 2 = 10
7. Define gravitational potential energy.

8. Define power.

9. Calculate the work done by a force of 30 N in lifting a load of 2kg to a height of 10m (g = 10ms-2).

10. A bullet of mass 20 g strikes a pendulum of mass 5 kg. Th e centre of mass of pendulum rises a vertical distance of 10 em. If the bullet gets embedded into the pendulum, calculate its initial speed

11. Is whole of the kinetic energy lost in any perfectly inelastic collision?

12. 5 x 3 = 15
13. Depict Δ kinetic energy = ΔU in potential energy - displacement graph for a spring.

14. State total lineal momentum is conserved in all collisions.

15. An object of mass 2 kg is taken to a height 5 m from the ground (g = 10 ms-2 ).
(a) Calculate the potential energy stored in the object.
(b) Where does this potential energy come from?
(c) What external force must act to bring the mass to that height?
(d) What is the net force that acts on the object while the object is taken to the height 'h'?

16. Let the two springs A and B be such that kA > kB, On which spring will more work has to be done if they are stretched by the same force?

17. A lighter particle moving with a speed of 10 ms-1 collides with an object of double its mass moving in the same direction with half its speed. Assume that the collision is a one dimensional elastic collision. What will be the speed of both particles after the collision?

18. 4 x 5 = 20
19. Arrive at an expression for power and velocity. Give some examples for the same.

20. What is inelastic collision? In which way it is different from elastic collision. Mention few examples in day to day life for inelastic collision.

21. Derive an expression for the potential energy of a body near the surface of the Earth.

22. A body of mass of 3 kg initially at rest makes under the action of an applied horizontally force of 10 N on a table with co-efficient of kinetic friction = 0.3, then what is the workdone by the applied force in 10s: