Chapter 4Force and Motion

(Don’t make life fun! Just run, run and run until you get your work done otherwise you will have none in the day of judgment under sun…!

Definitions

Physics Def. & MCQs 1 Dr. Sajid Ali Talpur

1. Motion: - When an object changes its position with respect to its surrounding it is said to be in motion.

2. Newton’s First Law of Motion: - it states that “A body continues its state of rest or

uniform motion unless an external force acts on it”

3. Inertia: -It is the property of matter by virtue of which it opposes any change in its state of rest or that of motion.

4. Force: -It is the agency that causes or tries to change the state of rest or that of the motion of the body.

5. Newton’s second law of motion: - According to it

“When an unbalanced force acts on a body it produces acceleration in the body in the direction of force which is directly proportional to the force and indirectly proportional to mass of the body”

6. Newton’s third law of motion: - It states that “Every action has an equal and opposite

reaction”

7. Weight: - Weight of the body is the gravitational pull of the earth on the body.

Physics Def. & MCQs 2 Dr. Sajid Ali Talpur

8. Tension: -When an object is suspended by a string the force that acts along the string and is equal in magnitude and opposite in direction to the weight is called tension.

9. Thrust: -A forcefully pushing force.

10. Up thrust: - It is the force that pushes things up in water.

11. Reaction: -The opposing force of action (which is the application of force)

12. Friction: -The resistive or opposing force to the motion of the object generated when the two surfaces or in contact.

13. Static Friction: -The friction between the body and the surface when the body is at rest

14. Kinetic or dynamic Friction: -When the body is in motion relative to the surface then the force of friction between the object and surface is of dynamic type.

15. Sliding Friction: -When a body slides on a surface the corresponding force of friction is called sliding friction.

16. Rolling Friction: -When a body rolls on a surface the corresponding force of friction is called rolling friction.

Physics Def. & MCQs 3 Dr. Sajid Ali Talpur

17. Limiting Friction: -The maximum static friction when the object is on the verge of slipping is called limiting friction.

18. Fluid Friction: -When a solid object moves through a fluid (viscous medium), it experience an opposing force on it, called fluid friction.

19. Resistance: -the force that prevents the motion.

20. Frame of Reference: -A set of coordinate axes in terms of which the position or movement may be specified or with reference to which physical phenomenon may be stated mathematically.

21. Momentum: - It is defined as the product of mass and velocity of the body.

22. Law of conservation of momentum: -The total momentum of an isolated system before and after collision remains conserved.

Physics Def. & MCQs 4 Dr. Sajid Ali Talpur

Multiple Choice Questions

1. Momentum =a) mass × velocity b) mass × acceleration c) force × velocity d) force × acceleration

2. Find the incorrect statement about force:a) its S.I unit is Newtonb) it always produces motionc) force and acceleration are directly proportional to each otherd) F=ma

Questions 3 - 10 Select from the terms below A) Newton’s first law of motion B) Newton’s second law of motion C) Newton’s third law of motion D) N.O.T

3. Every action has an equal and opposite reaction is the statement of:

4. Also known as law of inertia

5. Acceleration is directly proportional to force is the statement of:

6. Walking and firing of bullets are the examples of:

7. Acceleration is directly proportional to mass is the statement of:

Physics Def. & MCQs 5 Dr. Sajid Ali Talpur

8. Motion of boat obeys:

9. The flight of birds shown by the upward and downward motion of their wings is in accordance with:

10. Falling of leaves from plants on jerking is in accordance with:

11. Far walking it is not necessary:a) friction b) gravityc) smoothness d) N.O.T

12. The unit of momentum is:a) N b) N.mc) Nm- d) Nm-2

13. The maximum force of friction which just stops body from sliding or moving is called:a) rolling friction b) static frictionc) kinetic friction d) limiting friction

14. When force acting on a body is doubled its acceleration becomes:a) ½ b) ¼c) doubled d) quadrupled

15. Find the force acting on a body of mass 10kg moving with the acceleration of 5m/s2.a) 5N b) 15Nc) 30N d) 50N

Physics Def. & MCQs 6 Dr. Sajid Ali Talpur

16. What is mass of a body of weight 9.8Na) 1kg b) 1gc) 9.8kg d) 9.8g

17. How much acceleration will be produced in a body of 15kg if force of 30N acts on it?a) 1m/s2 b) 2m/s2

c) 3 m/s2 d) 3 m/s2

18. What is the mass of a body if the force of 20N produces acceleration of 5 m/s2

a) 3kg b) 4kgc) 15kg d) 400g

19. What is the weight of a body of mass 10kga) 10N b) 19.6Nc) 49N d) 98N

20. A stone weighing 2N is placed over wooden table. The friction between stone and the table is:a) 0.08N b) 0.8Nc) 8N d) N.O.T

21. A force of 54N acts on a stationary body for 2s and the body acquires velocity of 18m/s. the mass of body is:a) 6kg b) 8kgc) 18kg d) 32kg

Physics Def. & MCQs 7 Dr. Sajid Ali Talpur

22. A body weighing 19.6N is resting at a place. What force is needed to produce acceleration of 2 m/s2

a) 2N b) 4Nc) 9.8N d) 39.2N

Questions 23-35 Select from the terms below

A) True B) False

23. Mass and weight both have same unit

24. The weight of a body is always constant

25. m1v1 + m2v2 = m1u1 + m2u2 represents law of conservation of momentum

26. Weight is a scalar quantity

27. Friction is directly proportional to deceleration

28. Friction will not be produced if the two surfaces in contact are totally smooth.

29. Rolling friction is lesser than sliding friction

30. It is always necessary to apply force to stop moving object

31. The quality of matter of a body is called its mass

32. Action and reactions have equal magnitude but different direction

Physics Def. & MCQs 8 Dr. Sajid Ali Talpur

33. When an unbalanced force acts on a body it always produces acceleration

34. The friction during motion is called kinetic motion

35. It is dangerous to jump from moving train because of inertia.

Answer Key1 A 2 B 3 C4 A 5 B 6 C7 D 8 C 9 C10 A 11 C 12 B13 D 14 C 15 D16 A 17 B 18 B19 D 20 B 21 A22 B 23 B 24 B25 B 26 B 27 A28 A 29 A 30 A31 B 32 A 33 A34 A 35 A

Physics Def. & MCQs 9 Dr. Sajid Ali Talpur