1. Dynamics ( sometimes called) Kinematics Mechanics Lecture 4 6 th November 2014

2. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Dynamics ( sometimes called) Kinematics Mechanics Lecture 4 6 th November 2014

3. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Check basic definitions ScalarVectorUnits Distance How far you have gone Displacement Distance from home in a given direction m m with direction (compass etc) Speed How fast you are going Velocity How fast you are going in a given direction ms -1 ms -1 in specified direction Acceleration Rate of change of velocity vector ms -2 in specified direction

4. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Speed – easy stuff… If an object travels at constant speed v, for distance d in time t : v = d/t so d= v t and t=d/v If the speed does not remain constant then v=d/t represents an average speed over time t. This matters for speed cameras

5. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Graphing motion Mini- whiteboards – Displacement against time Velocity against time What does this graph tell us?

6. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Walking graphs. Displacement Time

7. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Walking graphs. Displacement Time What’s the story? Set off for the bus here

8. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Getting speed from distance graphs (1) Easy! Steady speed. v = s/t

9. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Getting speed from distance graphs (2) Variable speed Need to take the tangent at the time you are interested in and find its gradient. EMPA tip – 8cm * 8cm minimum

10. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Graphing motion What does the area under a velocity/time graph give us? What does this graph tell us?

11. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Card sort

12. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT The equations of motion, for constant acceleration in a straight line Five parameters can describe motion… s - displacement u - initial velocity v - final velocity a - acceleration t - time

13. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT These are the four “suvat” equations: v = u + at s = ½ (u + v) t s = u t + ½at 2 v 2 =u 2 + 2as So each one links four of the five parameters no s no a no v no t

14. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Where do these come from? We’ll see later! More important that you can use them systematically

15. Suvat –Systematically!

16. Some more practice

17. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Where do the suvat equations come from? Try to derive first two from thinking about a and s The third and fourth come from combining the first two

19. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT

20. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Free Fall Galileo’s ideas How to examine using modern methods?

22. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Graph this (in Excel)..\..\..\..\A levels\A level Physics\AS Physics\Unit 2\Dynamics\graph for NT book freefall data.xlsx..\..\..\..\A levels\A level Physics\AS Physics\Unit 2\Dynamics\graph for NT book freefall data.xlsx

23. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Using suvat with free-fall equations

24. Using suvat with free-fall equations - practice

25. Objectives Define basic parameters Describe motion graphically Derive two SUVAT equations Key Words Distance / Displacement Speed / Velocity Acceleration SUVAT Summary Four suvat equations Link the five parameters s u v a t Easy to use if you are systematic and consistent with coordinate systems. Unlikely to be tested on derivation