1. المحاضرة السابعة
The Laws of Motion

2. The Laws of Motion
Chapter 5

3. 5.1 The Concept of Force
The body is moving, When it change its position during a limited time.

4. 5.1 The Concept of Force
Types of Motion:

5. . Force is a vector quantity
5.1 The Concept of Force
. An object accelerates due to an external force.
. Force is a vector quantity

6. Definition of equilibrium
object is in equilibrium if:
The net force acting on the object is zero,
. The object remains at rest.
. or continues to move with constant velocity.

7. Measuring the Strength of a Force
It is convenient to use the deformation of a spring to measure force.

8. Newton ‘s laws of motion

9. FIRST NEWTON’s LAW
SECOND NEWTON’s LAW
THIRD NEWTON’s LAW

10. 5.2 Newton’s First Law Newton’s first law (law of inertia):
“ In the absence of external forces, an object at rest remains at rest and an object in motion continues in motion with a constant velocity (that is, with a constant speed in a straight line).”

11. . The SI unit of mass is the kilogram (Kg).
. Mass (m) is that property of an object that specifies how much resistance an object exhibits to changes in its velocity.
. The SI unit of mass is the kilogram (Kg).
. mass is a scalar quantity

12. 5.3 Mass

13. The Weight of an object (W):
Mass and weight
The Weight of an object (W):
. W = the gravitational force exerted on the object
. W varies with location
The Mass (m):
. Is the same everywhere

14. 5.4 Newton’s Second Law “The acceleration of an object is directly
proportional to the net force acting on it and inversely proportional to its mass”.
:is the net force
a : the acceleration.
m: mass.

15. 5.4 Newton’s Second Law
SI unit of force:
CGS unit of force:

16. 5.4 Newton’s Second Law

17. 5.4 Newton’s Second Law

18. Example 5.1

19. Question 2

20. Question 3

21. Problem 5.1

22. Problem 5.3

23. Problem 5.11

24. Problem 5.11

25. 5.5 The Gravitational Force and Weight
Gravitational force Fg :The attractive force exerted by the Earth on an object.
. The magnitude of Fg:
. Direction: Toward the center of earth

26. 5.5 The Gravitational Force and Weight
Nora
decided to live on the moon surface because her weight becomes list than her Wight on the surface of the earth? what is your opinion?

27. 5.5 The Gravitational Force and Weight

28. 5.5 The Gravitational Force and Weight

29. Problem 5.9

30. 5.6 Newton’s Third Law
“If two objects interact, the force F12 exerted by object 1 on object 2 is equal in magnitude and opposite in direction to the force F21 exerted by object 2 on object 1”:

31. . act on different objects . . and must be of the
5.6 Newton’s Third Law
“The action force is equal in magnitude to the reaction force and opposite in direction.”
The action and reaction forces:
. act on different objects .
. and must be of the
same type.

32. 5.6 Newton’s Third Law

33. 5.7 Some Applications of Newton’s Laws
.Tension Force
. Frictional Force: (in opposite of mosion direction)
. Elevator
. The Atwood Machine
. Inclined surface

34. Example 5.4 A Traffic Light at Rest

35. Example 5.4 A Traffic Light at Rest

36. Inclined Surface

37. One Block Pushes Another

38. Elevator

39. Example 5.8 Weighing a Fish in an Elevator

40. Example 5.8 Weighing a Fish in an Elevator

41. The Atwood Machine

42. Acceleration of Two Objects Connected by a Cord

43. Problem 21

44. Problem 21

45. Problem 23

46. Problem 24