Physics XI Karachi Board True and False - Chapter 3

Chapter 3 - Motion
1. The change of position of body in a particular direction is called its velocity.

2. The change of displacement with respect to time is called the velocity of the body.

3. The rate of change of position in a particular direction is called the displacement of covered by a body.

4. The total change in displacement of a body divided by the total change in time is called its velocity.

5. When the average and instantaneous values of acceleration of a body are equal then its acceleration is uniform.

6. First law of motion states that “a body remains at rest or continues to move with uniform velocity unless acted upon by an unbalanced force.

7. First law of motion is also called the law of inertia.

8. Force is that agent which produces or tends to produce the acceleration in the body.

9. Under the influence of constant force the body will move with constant speed

10. According to the second law of motion when constant force is applied on the body then the acceleration produced in it is directly proportional to the mass of the body.

11. Third law of motion states that “To every action there is always an equal but opposite reaction.”

12. Tension in string is reactionary force produced in it whenever it is subjected to pull.

13. The product of mass and velocity of the body is called its momentum.

14. The unit of linear momentum in SI unit is J.s.

15. The two falling bodies of different masses have the same momentum while they are striking the ground if they dropped from the same height.

16. In elastic collision between the two bodies, the total momentum and kinetic energy of the system remain constant.

17. If two identical masses are colliding elastically then after collision their velocities will interchange.

18. If a lighter body collides elastically with a massive body at rest then the massive body will start to move with a velocity equal to the double of the initial velocity of the first body.

19. Friction is self-adjusting force.

20. The frictional force always acts parallel to the surface in contact.


21. The direction of force of friction is always parallel to the direction of motion of the body.

22. The peculiar type of friction within the fluid is called its viscosity.

23. Sliding friction is always less than that of static friction.

24. Rolling friction is less than that of sliding friction.

25. Coefficient of kinetic friction is greater than that of the coefficient of static friction.

26. A small spherical body in the fluid is moving with uniform velocity, this velocity is called a terminal velocity.

27. On frictionless inclined plane the acceleration of the body is independent of its mass.

28. On frictionless (smooth) inclined plane where a = gsinq. If q = 0° then a = g.

29. On inclined plane ‘wcosq’ will always be equal to the normal reaction of the surface of inclined plane.

30. Fluid friction results when a solid object moves through a fluid.

31. Contact friction arises when on solid object is set into motion across the surface of another solid body.

32. The force needed to keep an object sliding is smaller than that required keeping it static.

33. 1 Newton = 105 dynes.

34. The law of conservation of momentum is equivalent to the Newton’s third law of motion.

35. The unit of tension in string in SI system is pound.

36. In inelastic collision only the momentum of the system is conserved.

37. Stoke’s law hold for motion through a viscous medium.

38. When force of gravity and viscous force become equal in magnitude during fall of a spherical body in fluid then the acceleration of that body is equal to acceleration due to gravity.

39. The terminal velocity of a spherical body in fluid is inversely proportional to the radius of the body.

40. When the friction between the surface of an inclined plane and the body on it is equal to the component of the weight of the body parallel to the plane then the object remains at rest on the inclined plane.