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#### Work, Energy and Power Book Back Questions

11th Standard

Reg.No. :
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Physics

Time : 00:45:00 Hrs
Total Marks : 30
5 x 1 = 5
1. A uniform force of (2$\hat { i }$+$\hat { j }$) N acts on a particle of mass 1 kg. The particle displaces from position (3$\hat { j }$+$\hat { k }$) m to (5$\hat { i }$+3$\hat { j }$) m. The work done by the force on the particle is

(a)

9 J

(b)

6 J

(c)

10 J

(d)

12 J

2. The work done by the conservative force for a closed path is

(a)

always negative

(b)

zero

(c)

always positive

(d)

not defined

3. If the potential energy of the particle is $\alpha -\frac { \beta }{ 2 } { x }^{ 2 }$ then force experienced by the particle is

(a)

F=$\frac { \beta }{ 2 } { x }^{ 2 }$

(b)

F=βx

(c)

F=-βx

(d)

F=-$\frac { \beta }{ 2 } { x }^{ 2 }$

4. A spring of force constant k is cut into two pieces such that one piece is double the length of the other. Then, the long piece will have a force constant of

(a)

$\frac{2}{3}$k

(b)

$\frac{3}{2}$k

(c)

3k

(d)

6k

5. Two equal masses m1 and m2 moving along the same straight line with velocities + 3 m/s and -5 m/s respectively collide elastically. Their velocities after the collision will be respectively

(a)

- 4 m/s and +4 m/s

(b)

+4 m/s for both

(c)

- 3 m/s and +5 m/s

(d)

- 5 m/s and + 3 m/s

6. 3 x 2 = 6
7. Explain how the definition of work in physics is different from general perception

8. Write the various types of potential energy. Explain the formulae.

9. A ball with a velocity of 5 ms-1 impinges at angle of 60° with the vertical on a smooth horizontal plane. If the coefficient of restitution is 0.5. find the velocity and direction after the impact.

10. 3 x 3 = 9
11. A weight lifter lifts a mass of 250 kg with a force 5000 N to the height of 5m
(a) What is the work done by the weight lifter?
(b) What is the work done by the gravity?
(c) What is the net work done on the object?

12. 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?

13. Consider an object of mass 2 kg moved by an external force 20 N in a surface having coefficient of kinetic friction 0.9 to a distance 10 m. What is the work done by the external force and kinetic friction? Comment on the result. (Assume g = 10 ms-2)

14. 2 x 5 = 10
15. Arrive at an expression for elastic collision in one Dimension and discuss various cases.

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