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#### Important questions - Laws of Motion

11th Standard

Reg.No. :
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Physics

Use blue pen Only

Time : 01:00:00 Hrs
Total Marks : 100

Part A

10 x 1 = 10
1. When a car takes a sudden left turn in the curved road, passengers are pushed towards the right due to

(a)

inertia of direction

(b)

inertia of motion

(c)

inertia of rest

(d)

absence of inertia

2. An object of mass m held against a vertical wall by applying horizontal force F as shown in the figure.The minimum value of the force F is

(a)

Less than mg

(b)

Equal to mg

(c)

Greater than mg

(d)

Cannot determine

3. A vehicle is moving along the positive x direction, if sudden brake is applied, then

(a)

frictional force acting on the vehicle is along negative x direction

(b)

frictional force acting on the vehicle is along positive x direction

(c)

no frictional force acts on the vehicle

(d)

frictional force acts in downward direction

4. When the object is moving at constant velocity on the rough surface

(a)

net force on the object is zero

(b)

no force acts on the object

(c)

only external force acts on the object

(d)

only kinetic friction acts on the object

5. When an object is at rest on "the inclined rough surface

(a)

static and kinetic frictions acting on the object is zero

(b)

static friction is zero but kinetic friction is not zero

(c)

static friction is not zero and kinetic friction is zero

(d)

static and kinetic frictions are not zero

6. The centrifugal force appears to exist

(a)

only in inertial frames

(b)

only in rotating frames

(c)

in any accelerated frame

(d)

both in inertial and non-inertial frames

7. A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle. The motion of the particle takes place in a plane. It follows that

(a)

Its acceleration is constant

(b)

Its velocity is constant

(c)

Its K.E. is contatnt

(d)

It moves in a straight line

8. Dimensions of impulse are same as that of

(a)

Force

(b)

Momentum

(c)

Energy

(d)

Acceleration

9. A machine gun has mass 15 kg. It fires 15 g bullet at the rate of 200 bullets per minutes with a speed of 150 m/s. Then the recoil velocity of the gun is,

(a)

20 ms-1

(b)

15 ms-1

(c)

150 ms-1

(d)

0.2 ms-1

10. How many degrees make a one newton?

(a)

102 dyne

(b)

202 dyne

(c)

105 dyne

(d)

205 dyne

11. Part B

10 x 2 = 20
12. Give examples for inertia frames

13. Find the acceleration when multiple forces act on the body?

14. Explain cause and effect by Newton's second law.

15. What are non-inertial frame of reference? Explain with example.

16. Will the momentum remain conserved if some external force acts on the system.

17. "Jumping on a cemented floor receives more injuries than on the sand" - Given reason.

18. Why do the blades of an electric fan continue to rotate for sometime after the current is switched off?

19. A ball of mass 0.20kg hits a wall at an angle of 45° with a velocity of 25 m/s. If the ball rebounds at 90° to the direction of incidence, calculate the change in momentum of the ball. Calculate (i) Impulse, (ii) Force, (iii) Maximum force.

20. Consider a circular road of radius 20 meter banked at an angle of 15 degree. With what speed a car has to move on the turn so that it will have safe turn?

21. A body of mass 100 kg is moving with an acceleration of 50 cm s-2. Calculate the force experienced by it.

22. Part C

10 x 3 = 30
23. Explain the concept of inertia. Write two examples each for inertia of motion, inertia of rest and inertia of direction

24. What is the meaning by 'pseudo force'?

25. Explain briefly how will you apply Newton's second law to a mango (mass 400 g) hanging from a tree.

26. The force that should be applied a body of mass 20 kg. It moves upward with an acceleration of 4 ms-2. Find the force in the vacuum.

27. A force of 20 N is inclined to the vertical at an angle of 60°. Find the acceleration it produces in a body of mass 500 g which moves in the horizontal direction.

28. Explain with example how earth can be treated as both inertial and' non-inertial frame of reference?

29. Draw and explain the variations of force of friction vs applied force graphically.

30. The diagram shows an estimated force-time graph for a baseball struck by a bat. Then find
(i) Impulse
(ii) Force
(iii) Maximum force

31. A mass of 6 kg is suspended by a rope of length 2m from a ceiling. A force of 50N in the horizontal direction is applied at the midpoint of the rope as shown in the figure. What is the angle the rope makes with the vertical is equlllbrium? Take g = 10 ms-2. Neglect mass of the rope.

32. As shown in the diagram, three masses m, 3m and Sm connected together lie on a frictionless horizontal surface and pulled to the left by a force F. The tension T1 in the first string is 24N. Find

(i) acceleration of the system
(ii) tension in the second string and
(iii) force F

33. Part D

8 x 5 = 40
34. Briefly explain 'centrifugal force' with suitable examples.

35. Explain the need for banking of tracks.

36. What is the reading shown in spring balance?

37. Write the Salient features of Static and Kinetic friction

38. What happens to the object at rest if (i) fs = 0 (ii) fs = Fext (iii) fs = max.

39. Derive an expression for the acceleration of the body sliding down a frictionless surface.

40. As shown In the diagram, three blocks connected together lie on a horizontal frictionless table and pulled to the right with a force F = 50N. If m1 = 5 kg, m2 = 10 kg and m3 = 15 kg. Find the tensions T1 and T2.

41. Identify the internal and external forces acting on the following systems.
(a) Earth alone as a system
(b) Earth and Sun as a system
(c) Our body as a system while walking
(d) Our body + Earth as a system