2. Lesson 18

3. OBJECTIVES Describe the force exerted by a battery- powered fan car. Describe the motion of a fan car Determine the effect of a constant force on the speed of a fan car Calculate a fan car’s average speed at different times as it moves along a path

4. Getting Started What does the term “average speed” mean? Average speed refers to the distance an objects moves in a given time. How do you calculate it? Average speed = Distance Time

5. Getting Started A car travels 100 meters (m) in 2 seconds. What is its speed? Speed = Distance/Time Speed = 100 m/ 2 seconds Speed = 50 m/s

6. Getting Started A car travels 100 meters (m) in 2 seconds. What is its speed? Speed = Distance/Time Speed = 100 m/ 2 seconds Speed = 50 m/s

7. Getting Started A jogger runs 50 meters in 25 seconds. What is the jogger’s speed? Speed = Distance/ Time Speed = 50 m / 25 s Speed = 2 m/s

8. Vocabulary – Lesson 18 Speed The rate at which an object changes its position over time or how fast something is moving distance traveled time traveled Acceleration When unbalanced forces act on an object, the object speeds up or slows down. The rate at which speed changes

9. Vocabulary Average Speed The distance an object moves divided by the time it takes to move that distance. Speed = Distance / Time Rate A measure of the way a quantity changes over time.

10. Vocabulary Inertia The tendency for objects to maintain their motion when no forces act on them Balanced Force Action of equal forces on an object in opposite directions (cancel each other out so net force is zero)

11. Vocabulary Unbalanced Force Forces that produce a non zero net force, which changes an object’s motion in the direction of the greater force.

12. Vocabulary – Lesson 18 Newton’s first law of motion – (inertia) –An object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless acted on by an unbalanced force

13. Vocabulary Newton’s Second Law of Motion - Force = mass x acceleration -An object acted upon by a force, will accelerate in the direction of that force. Acceleration depends on the mass of the object and the force action on the object.

14. Vocabulary Newton’s Third Law of Motion -For every action, there is an equal but opposite reaction. If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first.

15. Notes Speed is the rate at which an object changes its position over time and is calculated as: Speed = Distance/Time

16. Notes Average speed is calculated as Total distance traveled / Total time traveled An object that moves with changing speed is accelerating. Acceleration is the rate at which the speed changes.

17. Notes When an unbalanced force acts on an object, the object will accelerate, or change its speed. The acceleration can be a change in speed OR a change in direction of the motion of the cars.

18. Notes The greater the unbalanced force, the greater the acceleration. This is summarized by Newton’s 2 nd Law of motion which states : Force = Mass x Acceleration

19. Notes If unbalanced force is parallel to motion of an object, only the speed changes If force is in same direction of the emotion, the speed will increase. If force is in opposite direction, the speed will decrease.

20. Notes If a constant unbalanced force acts on an object, it will have a constant acceleration, so there will be a steady change in speed of the object.

21. Notes Inertia is the tendency for objects to maintain their motion when no forces act on them. (Newton’s 1 st Law of Motion) This is why if you push something, it will keep moving a small amount of time. The force of friction will cause it to stop.

22. Notes The motion of the car can be described in transformations: Your hand pushes the car and gives it KE. After you push, the car still has KE but friction works against the motion and eventually changes the KE into heat.

23. Notes As the car loses KE, it slows down. When all KE has been converted to heat, the car stops.

24. Notes When the fan is used, the fan pushes air through the blades. The air pushes on the fan that is attached to the car. The air goes in one direction, the car in the opposite direction. This is an example of Newton’s 3 rd Law of Motion which states “For every action, there is an equal and opposite reaction”.

25. Notes When the fan is on, a constant unbalanced force accelerates the car forward and the car moves with increasing speed.

26. Lesson 18

27. Question – Lesson 18 How does the speed of a fan car change at.4 m intervals across a distance of 2 meters?

28. Lesson 18 If _________________,then __________ because _________________.

29. SAFETY KEEP YOUR FINGERS AWAY FROM THE MOVING FAN BLADES!!!!

30. Lesson 18 Materials 1. 2. 3.

31. Lesson 18

32. Time and Distance Data for the Fan Car L 18

33. Lesson 18