Chapter Introduction Lesson 1 Motion Lesson 2 Forces Lesson 3 Types of Forces

1. Chapter Introduction Lesson 1 Motion Lesson 2 Forces Lesson 3Types of Forces Lesson 4Newton’s Laws Chapter Wrap-Up

2. How do forces change the motion of objects?

3. Motion • Essential Question • How is an object’s motion related to speed, velocity, and acceleration?

4. Motion • Distance • Position • Motion • Speed • Velocity • Acceleration

5. What is motion? • When you explain to your friend how to get to your house, you most likely will tell them direction – the way to go to get there. • You most likely will tell them distance. • Distance is the length between two places.

6. What is motion? (cont.) • Using direction and distance, can help you identify the position of something. • Position is the location of an object compared with things around it.

7. What is motion? (cont.) • A complete description of your position includes a distance, a direction, and a reference point – a starting point that can be used to locate a place or thing.

8. What is motion? (cont.) • Motion is a change in an object’s position compared to fixed objects around it. • The man in the boat is not in motion compared to his fishing pole. He is in motion compared to the buoy.

9. What is motion? (cont.) • When riding your bike, in relation to the bike, you are not moving. • However, the trees and houses you pass appear to move backward. This is known as apparent motion – when things appear to an observer to be moving but are not actually changing position. • You use apparent motion to determine what direction and how fast you are going.

10. What is speed? • Speed is how fast an object’s position changes with time at any given moment. • Units of speed are expressed in units of distance per unit of time. • Ex. Meters per second (m/s) or miles per hour (mph).

11. What is speed? (cont.) • Constant speed is a change of position in which the same distance is traveled each second. • Ex. Look at the figure below. The same distance is traveled in the same amount of time.

12. What is speed? (cont.) • Most moving objects do not travel at the same speed at all times. • Ex. In a car, you are stopping, starting and passing other cars. • When the car’s speed changes, it moves a different distance each period of time.

13. What is speed? (cont.) • Because objects do not travel at the same speed at all times, it is useful to calculate an average speed. • Average speed is the total distance traveled divided by the total amount of time.

14. What is speed? (cont.) • Graphs that show comparisons between distance and time are called distance-time graphs. • Constant speed is shown as a straight line on a distance-time graph.

15. What is speed?(cont.) • You can use distance-time graphs to compare the motion of two different objects. • The steeper line indicates a faster speed.

16. What is speed?(cont.) • When an object is not traveling at constant speed, the graph is not a straight line but a curved line.

17. What is velocity? • Velocity is a description of a moving object’s speed and direction. • Ex. If a is car traveling south with a speed of 70mph, its velocity would be 70mph south.

18. What is velocity? (cont.) • The velocity of an object can be represented by an arrow. • A greater speed is shown by a longer arrow. • The arrow points in the direction of the object’s movement.

19. What is velocity?(cont.) • Velocity changes when: • the speed of an object changes • the direction that the object moves changes • or both the speed and the direction change

20. What is velocity? (cont.) • Speed and velocity are often confused for the same thing but they are not. • Speed tells how fast something is going. • Velocity tells how fast something is going and in what direction.

21. What is acceleration? • Acceleration is a change in the velocity of an object over time. • An object accelerates when its velocity changes as a result of: • increasing speed. • decreasing speed. • or a change in direction.

22. What is acceleration? (cont.) • Acceleration has a direction and can be represented by an arrow. • The length of the arrow indicates the amount of acceleration. • The direction of the arrow depends on whether velocity increases or decreases.

23. What is acceleration?(cont.) • Acceleration is a change in velocity divided by the time interval during which the velocity changes.

24. What is acceleration? (cont.) • When an object speeds up, the acceleration is in the same direction as the motion and is positive. • Ex. Object goes from 0m/s to 6m/s in 3 sec. acceleration =(6-0) ÷ 3 = 6 ÷ 3 = 2m/s2

25. What is acceleration? (cont.) • When an object slows down, the acceleration is in the opposite direction as the motion and is negative. • Ex. Object goes from 6m/s to 0m/s in 3 sec. acceleration =(0-6) ÷ 3 = -6 ÷ 3 = -2m/s2 • Which could be stated as deceleration at 2m/s2

26. How can you graph acceleration? • A speed-time graph shows how speed changes over time. • A speed-time graph has time on the horizontal axis—the x-axis, and speed on the vertical axis—the y axis.

27. How can you graph acceleration? (cont) • An object at rest is not moving, so its speed is always zero.

28. How can you graph acceleration?(cont) • For an object moving at constant speed, the speed-time graph is a horizontal line.

29. How can you graph acceleration?(cont) • The line on the speed-time graph for an object that is speeding up has an upward slope.

30. How can you graph acceleration? (cont) • The line on the speed-time graph for an object that is slowing down has a downward slope.

31. The total distance traveled divided by the total time taken to travel that distance is known as which of these? A. speed B. constant speed C. instantaneous speed D. average speed

32. How is constant speed represented on a distance-time graph? A. a wavy line B. a crooked line C. a straight line D. a curved line

33. A hot-air balloon rises at a rate of 3km/h. What is its velocity? A. 3km/h, upward B. 3mph, upward C. 3 km/h D. 3km/h/h

34. Forces • Essential Question • What effect do forces have on objects?

35. Forces • Net force • Balanced forces • Unbalanced forces • Force • Contact force • Noncontact force

36. What are forces? • Force is a push or pull exerted by one object on another, possibly causing a change in motion. • Forces can cause: • A moving object to accelerate or decelerate. • An object to start moving. • An object to change direction. • An object to stop moving.

37. What are forces? (cont.) • Contact force is a force that is exerted only when objects are touching. • Ex. baseball bat hitting a baseball or fingers striking keyboard of computer • Noncontact force is a force exerted when objects are not touching. • Ex. Magnetic force, like a compass needle or gravitational force, Earth around the Sun

38. How do forces affect each other? • Net force is the combination of all forces acting on an object. • The net force depends on the directions of the forces applied to an object. • Because forces have direction, you have to specify a reference direction when you add forces.

39. How do forces affect each other? (cont.) • A force moving in the reference direction is positive, and a force in the opposite direction is negative. • When the forces applied to an object act in the same direction, the net force is the sum of the individual forces.

40. How do forces affect each other? (cont.) • When forces act in opposite direction on an object, the net force is still the sum of the forces. • The net force is the sum of the positive and negative forces.

41. What are balanced and unbalanced forces? • Balanced forces are forces that act together on an object without changing its motion. • Ex. • Unbalanced forces are forces that do not cancel each other out and that cause an object to change its motion. • Ex.

42. Which refers to forces that combine and form a net force that is not zero? A. balanced forces B. inertia C. net force D. unbalanced forces

43. When equal forces act on an object in opposite directions, what is the net force on the object? A. zero B. one C. equal D. balanced

44. Which changes when unbalanced forces act on an object? A. color B. mass C. motion D. weight

45. Types of Forces • Essential Question • What are the forces that act upon objects?

46. Types of Forces • Gravity • Friction • Air resistance • Elastic force • Tension force

47. What is gravity? • Gravity is the force of attraction among all objects. • Sir Isaac Newton developed the law of universal gravitation in the late 1600s. • The law states that all objects are attracted to each other by a gravitational force.

48. What is gravity? (cont.) • The strength of force depends on the mass of each object and the distance between them.

49. What is gravity? (cont.) • Weight is the gravitational force exerted on an object. • Near Earth’s surface, an object’s weight is the gravitational force exerted on the object by Earth. • Because weight is a force, it is measured in newtons.

50. What is gravity? (cont.) • An object’s weight is proportional to its mass. • Near Earth’s surface, the weight of an object in newtons is about ten times its mass in kilograms.