Work, Energy and Power Sample Questions

11th Standard

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. A particle of mass m is being rotated on a vertical circle of radius r. If the speed of particle at the highest point be v, then

(a)

mg=$\frac{mv^{2}}{r}$

(b)

mg>$\frac{mv^{2}}{r}$

(c)

mg<$\frac{mv^{2}}{r}$

(d)

mg≥$\frac{mv^{2}}{r}$

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

(a)

1

(b)

0

(c)

$\alpha$

(d)

-1

3. The potential energy of a system increases, if work is done

(a)

by the system against a conservative force

(b)

by the system against a non-conservative force

(c)

upon the system by a conservative force

(d)

upon the system by a non- conservative force

4. 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)

$\sqrt{gR}$

5. Two equal masses m1 and m2 are moving along the same straight line with velocities 5ms-1 and -9 ms-1 respectively. If the collision is elastic, then calculate the velocities after the collision of m1 and mrespectively

(a)

-4ms-1 and 10 ms-1

(b)

10ms-1 and 0 ms-1

(c)

-9ms-1 and 5 ms-1

(d)

5ms-1 and 1 ms-1

6. 5 x 2 = 10
7. Define Potential energy. Write the expression of it.

8. Define gravitational potential energy.

9. Explain the characteristics of elastic and inelastic collision.

10. 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.

11. A car starts from rest and moves on a surface with uniform acceleration. Draw the graph of kinetic energy versus displacement. What information you can get from that graph?

12. 5 x 3 = 15
13. Obtain graphically and mathematically work done by a variable force.

14. What is mechanical energy? What are its two types?

15. What does the work-kinetic energy theorem imply?

16. Two objects of masses 2 kg and 4 kg are moving with the same momentum of 20 kg m s-1
(a) Will they have same kinetic energy?
(b) Will they have same speed?

17. 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)

18. 4 x 5 = 20
19. Explain with graphs the difference between work done by a constant force and by a variable force

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. What is meant by elastic potential energy? Drive an expression for the elastic potential energy of the spring.

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: