1. 02 Mechanics BY HEI MAN KWOK

2. 2.1 KINEMATICS

3. Definitions Displacement: distance moved in a particular direction – vector; SL Unit: m; Symbol: s Velocity: rate of change of displacement (has a direction) – vector; SL Unit: ms¯¹; Symbol: v or u Speed: rate of change of distance – scalar; SL Unit: ms¯¹; Symbol: v or u Acceleration: rate of change of velocity (change of direction or velocity) – vector; SL Unit: ms¯²; Symbol: a

4. Instantaneous vs Average Instantaneous: at a particular point in time Average: taken over a period of time AverageInstanteous Speed Velocity AccelerationDoesn’t exist

5. Conditions of SUVAT/ Uniformly Accelerated Motion

6. Free-fall

7. Sketch + label, calculate and interpret Distance - time Displacement – time Velocity – time Acceleration – time Eg. Bouncing ball and free-fall

8. Relative Velocity in 1D and 2D

9. 9.1 PROJECTILE MOTION

10. 2.2 FORCES AND DYNAMICS

11. Weight (a type of force) Weight = mass x gravity W = mg W = mass x 9.81

12. Forces Force in Newtons (N); a vector quantity 1.Tension 2.Contact (Normal if at 90 degrees) 3.Weight 4.Friction 5.Upthrust 6.Air resistance

13. Determining Resultant Force Use sin cos tan and phytagorous if needed Make sure the forces are only in opposite directions before final calculation

14. Newton’s First Law of Motion A body will remain at rest or moving with constant velocity unless acted upon by an unbalanced force Eg. Mass on a string, parachutist,

15. Translational Equilibrium All forces are balanced Center of force will not move however the mass can rotate around the center

16. Newton’s Second Law of Motion

17. Linear Momentum and Impulse

18. Force-time graph

19. Law of Conservation of Linear Momentum Linear momentum is conserved (always the same) for a system of isolated bodies without any external forces acting upon the two objects

20. Newton’s Third Law of Motion

21. 2.3 WORK, ENERGY AND POWER

22. Work Work done = force x distance moved in the direction of the force If displacement is not in the direction of the force – change one of them Interpret a force – displacement graph

23. Energy and Principle of Conversation of Energy Energy is the quantity that enables body A to do work on body B When body A does work on body B, energy is transferred from body A to body B (be able to describe energy transformation) Principle of Conversation of Energy – Energy cannot be created nor destroyed – it can only be changed and transferred from one form to another

24. Kinetic Energy and Gravitational Potential Energy

25. Elastic and Inelastic Collisions Elastic Collisions: KE and mv (p) are conserved Inelastic Collisions: two bodies stick tgt and according to the law of energy conservation; wd squashing the balls = energy lost as KE Eg. Explosion – energy to initiate an explosion comes from the chemical energy contained in the explosive = energy gained in KE of the ball

26. Power and Efficiency

27. 2.4 UNIFORM CIRCULAR MOTION