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#### Nature of Physical World and Measurement-2marks

11th Standard

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 70
Part-A
35 x 2 = 70
1. Explain how the definition of work in physics is different from general perception

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

3. Write the differences between conservative and Non-conservative forces. Give two examples each.

4. Explain the characteristics of elastic and inelastic collision.

5. Define the following
a) Coefficient of restitution
b) Power
c) Law of conservation of energy
d) loss of kinetic energy in inelastic collision

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

7. 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.

8. A bob of mass m is attached to one end of the rod of negligible mass and length r, the other end of which is pivoted freely at a fixed center O as shown in the figure. What initial speed must be given to the object to reach the top of the circle? (Hint: Use law of conservation of energy). Is this -speed less or greater than speed obtained in the section 4.2.9?

9. Two different unknown masses A and B collide. A is initially at rest when B has a speed v. After collision B has a speed v/2 and moves at right angles to its original direction of motion. Find the direction in which A moves after collision

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. A spring which is initially in un-stretched condition, is first stretched by a length x and again by a further length x. The work done in the first case W1 is one third of the work done in second case W2True or false?

12. Which is conserved in inelastic collision? Total energy (or) Kinetic energy?

13. Is there any network done by external forces on a car moving with a constant speed along a straight road?

14. 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?

15. A charged particle moves towards another charged particle. Under what conditions the total momentum and the total energy of the system conserved?

16. A box is pulled with a force of 25 N to produce a displacement of 15 m. If the angle between the force and displacement is 30°, find the work done by the force.

17. An object of mass 2 kg falls from a height of 5 m to the ground. What is the work done by the gravitational force on the object? (Neglect air resistance; Take g = 10m s-2).

18. An object of mass m = 1 kg is sliding from top to bottom in the fiictionless inclined plane of inclination angle 9 = 30° and the length of inclined plane is 10 m as shown in the figure. Calculate the work done by gravitational force and normal force on the object.Assume acceleration due to gravity, g = 10m s-2

19. If an object of mass 2 kg is thrown up from the ground reaches a height of 5 m and falls back to the Earth (neglect the air resistance). Calculate
(a) The work done by gravity when the object reaches 5 m height
(b) The work done by gravity when the object comes back to Earth
(c) Total work done by gravity both in upward and downward motion and mention the physical significance of the result.

20. A variable force F = kx2 acts on a particle which is initially at rest. Calculate the work done by the force during the displacement of the particle from x = 0 m to x = 4 m. (Assume the constant k = IN m-2)

21. A force $\vec F=\vec i+2\vec j+3\vec k$ k acts on a particle and displaces it through a distance $\vec S=4\vec i+6\vec j$Calculate the work done if force and work done are in the same direction

22. An object of mass 1 kg is falling from the height h = 10m. Calculate
(a) The total energy of an object at h = 10 m.
(b) Potential energy ofthe object when it is at h = 4 m.
(c) Kinetic energy of the object when it is at h = 4 m.
(d) What will be the speed of the object when it hits the ground?
(Assume g = 10 m s-2)

23. An object of mass m is projected from the ground with initial speed v0. Find the speed at height h.

24. Water in a bucket tied with rope is whirled around in a vertical circle of radius 0.5 m. Calculate the minimum velocity at the lowest point so that the water does not spill from it in the course of motion. (g= 10 ms-2)

25. Calculate the energy consumed in electrical units when a 75 W fan is used for 8 hours daily for one month (30 days).

26. A bullet of mass 50 g is fired from below into a suspended object of mass 450 g. The object rises through a height of 1.8 m with bullet remaining inside the object. Find the speed of the bullet. Take g = 10 ms-2.

27. Show that the ratio of velocities of equal masses in an inelastic collision when one of the masses is stationary is $\frac { { v }_{ 1 } }{ { v }_{ 2 } } =\frac { 1-e }{ 1+e }$

28. A particle moves along X- axis from x = 0 to x = 8 under the influence of a force given by F = 3x2 - 4x + 5. Find the work done in the process.

29. A body of mass 10 kg at rest is subjected to a force of 16N. Find the kinetic energy at the end of 10 s.

30. A body of mass 5 kg is thrown up vertically with a kinetic energy of 1000 J. If acceleration due to gravity is 10 ms-1, find the height at which the kinetic energy becomes half of the original value.

31. Two bodies of mass 60 kg and 30 kg move in the same direction along straight line with velocity 40 cms-1 and 30 cms-1 respectively suffer one dimensional elastic collision. Find their velocities after collision.

32. A particle of mass 70 g moving at 50 cms-1 is acted upon by a variable force as shown in the figure. What will be its speed once the force stops?

33. A particle strikes a horizontal frictionless floor with a speed u at an angle $\theta$  with the vertical and rebounds with the speed v at an angle $\phi$ with an vertical. The coefficient of restitution between the particle and floor is e. What is the magnitude of v?

34. A particle of mass m is fixed to one end of a light spring of force constant k and unstretched length I. It is rotated with an angular velocity w in horizontal circle. What will be the length increase in the spring?

35. A gun fires 8 bullets per second into a target X. If the mass of each bullet is 3 g and its speed 600 s-1. Then, calculate the power delivered by the bullets.