Devil physics The baddest class on campus Pre-IB Physics

1. Devil physicsThe baddest class on campusPre-IB Physics

2. Giancoli Lessons 4-1 to 4-6dynamics: force and motion

3. Objectives: • State Newton’s First Law of Motion. • Explain the difference between an accelerated reference frame and an inertial reference frame. • State the ‘chemistry’ and the ‘physics’ definitions of mass. • Apply Newton’s First Law of Motion to solve problems.

4. Objectives: • State Newton’s Second Law of Motion. • Given several different forces acting on an object, find the net force. • State the SI unit for force and give it’s component base SI units. • Apply Newton’s Second Law of Motion to solve problems.

5. Objectives: • State Newton’s Third Law of Motion. • Explain the terms normal force, reaction forceandcontact force. • Apply Newton’s Third Law of Motion to solve problems.

6. Force – Aristotle  Galileo • Push or pull on an object • May or may not produce motion • For a given object, the force needed to move the object may change based on the surface it’s resting on • For a body already in motion, force is needed to change the direction or speed

7. Newton’s First Law of Motion

8. Newton’s First Law of Motion • Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force

9. Newton’s First Law of Motion • Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force • Everything that has mass • Just about everything except light and heat

10. Newton’s First Law of Motion • Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force • Inertia – tendency of a body to maintain its state of rest or uniform motion • First law also called law of inertia

11. Newton’s First Law of Motion • Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force • Important concept to remember for second law • Something must happen for an object to change direction

12. Newton’s First Law of Motion • Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force • Force is required to change a body’s state of rest • Force is required to change a body’s uniform straight-line speed

13. Reference Frames • Accelerating Reference Frame • Coffee on the dashboard • Inertial Reference Frame • Fixed, or at constant velocity, in space • Can anything on earth really be called an inertial reference frame?

14. Reference Frames • Accelerating Reference Frame • Coffee on the dashboard • Inertial Reference Frame • Fixed, or at constant velocity, in space • Can anything on earth really be called an inertial reference frame? • Rotation of the earth • Orbit of the earth

15. Mass • Not a Catholic church service • Chemistry - Quantity of matter

16. Mass • Not a Catholic church service • Chemistry - Quantity of matter • Physics – measure of the inertia of a body

17. Mass vs Weight • What’s the difference?

18. Mass vs Weight • Mass • Property of the body itself • Quantity of matter • Measure of inertia • Weight • Property of a body in relation to other bodies • Gravitational attraction between two bodies • It is dependent on proximity to other bodies (gravity) • Weight is a force

19. Newton’s Second Law of Motion

20. Newton’s Second Law of Motion • The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.

21. Newton’s Second Law of Motion • The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object. • Movement • Inertia has been overcome • Change in speed • Change in direction

22. Newton’s Second Law of Motion • The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.

23. Newton’s Second Law of Motion • The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.

24. Newton’s Second Law of Motion • The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.

25. Weight as a Force • Weight is a Force • F = ma • What’s the a?

26. Weight as a Force • Weight is a Force • F = ma • What’s the a? • Acceleration due to gravity • g = 9.81 m/s2

27. Force - Units • Weight is a Force • F = ma • Unit of mass is the kilogram • Units for acceleration are m/s2 • Units for ma are kg·m/s2 • This is called a Newton (N) • 1 N = 1 kg·m/s2

28. Newton’s Third Law of Motion

29. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first.

30. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • Consider a book on a table • The book has weight, so it is exerting a force on the table • Since the book isn’t moving, the table is exerting an equal an opposite force on the book • The table is said to be exerting a reaction force, contact force or normal force on the book

31. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • Consider a book on a table • If the book has a mass of 5kg, what force is the table exerting on the book?

32. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • Consider a book on a table • If the book has a mass of 5kg, what force is the table exerting on the book? • F = mg • F = (5) (9.81) = 49.1 N

33. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • What about 100 books on the table?

34. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • What about 100 books on the table? • F = mg • F = (100) (5) (9.81) = 4,910 N

35. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • What about 1000 books on the table?

36. Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second exerts an equal and opposite force on the first • What about 1000 books on the table? • This would probably exceed the capability of the table to produce a normal force equal to the force of the weight of the books • As the table broke, the books would accelerate in the downward direction.

37. Example 4-5 • Contact force • Normal force • Sum of the forces

38. Summary Review: • Can you state Newton’s First Law of Motion? • Can you explain the difference between an accelerated reference frame and an inertial reference frame? • Can you state the ‘chemistry’ and the ‘physics’ definitions of mass? • Can you apply Newton’s First Law of Motion to solve problems?

39. Objectives: • Can you state Newton’s Second Law of Motion? • Given several different forces acting on an object, can you find the net force? • Can you state the SI unit for force and give it’s component base SI units? • Can you apply Newton’s Second Law of Motion to solve problems?

40. Objectives: • Can you state Newton’s Third Law of Motion? • Can you explain the terms normal force, reaction forceandcontact force? • Can you apply Newton’s Third Law of Motion to solve problems?

41. Questions?

42. Homework Part A, #1-10 Part B, #11-19