1. Effects of Forces Change shapeChange shape

2. Effects of Forces Change shapeChange shape

3. Change of Shape

4. extension Force is directly proportional to extension

5. When force doubles, the extension doublesWhen force doubles, the extension doubles F α xF α x F x = constant Hooke’s Law

6. Force is directly proportional to extension F1F1 x1x1 = F2F2 x2x2 m1m1 x1x1 = m2m2 x2x2

7. What if we put more weights than we did? Limit of proportionality See p.23 SQ and Key PointsSee p.29 question 5

8. Effects of Forces Change the state of motionChange the state of motion –Move from rest –Speed up –Slow down –Stop –Change its direction

9. Balanced forces

10. Balanced Forces The book stays still!

11. Balanced Forces The airplane moves forwards at constant speed!

12. Balanced Forces The car moves at constant speed! Drag Friction Thrust

13. Unbalanced Forces The car moves from rest. The car speeds up.

14. Unbalanced Forces The car slows down to stop. The car slows down. See p.25 SQ and Key PointsSee p.27 SQ and Key Points