Newton's laws of motion and concepts related to forces and motion are discussed. Key points include: Newton's 3 laws of motion, that force is a vector quantity with magnitude and direction, and concepts like impulse, momentum, conservation of energy and momentum. Newton's 2nd law, which relates force, mass and acceleration, is identified as particularly relevant for understanding acceleration.

1. Newton’s Laws And forces, vectors, gravity, momentum, impulse and moments

2. Newton’s First Law Objects at rest remain at rest Objects in motion remain in motion UNTIL YOU APPLY A FORCE

3. Newton’s Second Law F = ma What forces are important in sports?

4. Newton’s Third Law For every action there is an equal and opposite reaction. But do they act on the same body?

5. Vector Force is a vector - ? It has a magnitude and a direction. This allows forces to be cancelled out. Force brings about acceleration Which law relates to that? Newton’s 2 nd Law F=ma

6. Non-parallel forces Can add vectors in different directions: c 2 = a 2 + b 2 ; angle x = tan -1 a/b x Resultant force a b c

7. Vectors Remember: the resultant force is not a new force It is the sum of the 2 components Use either the resultant or component in any calculation, not both!

8. Newton What is a Newton? Unit 1N = force that accelerates 1kg mass by 1ms -2

9. weight What’s the weight of 1 litre of water? 1kg is the mass The weight = mass x g g is the gravitational field strength g = 10 N kg -1 or 9.81 N kg -1 (more accurately) Weight of 1 litre of water is 10N or 9.81N

10. Quiz What is my acceleration due to weight? 9.81 ms -2 What is your acceleration due to weight? 9.81 ms -2 What about the marker? 9.81 ms -2 Acceleration due to weight is always g

11. Mass Amount of matter Measure of inertia Inertia is the resistance to acceleration Mass attracts gravity Gravitational force is directly proportional to mass Note: Gravitational force is inversely proportional to distance 2 between 2 points

12. Quiz As one moves away from the centre of the earth, his/her weight decreases. At 3000m, g = 9.8009 N kg -1 What if we throw shot put at 3000m? What if we run marathon at 3000m? At 3000m, oxygen pressure is reduced by more than 10% Always consider other factors!

13. Impulse Momentum = mass x velocity Since F = ma and a = ∆ v / t , F = m ∆ v / t Therefore F t = m ∆v, or Impulse = change of momentum The larger the impulse, the greater is the change in velocity. Application?

14. Impulse Hence, to increase velocity, we either increase F or t (time of contact). Remember, F = m ∆ v / t To reduce impact, encourage soft landing Use cushioning, bend joints, etc

15. Conservation of energy Energy is always conserved Regardless of whether you can observe Mechanical energy is not always conserved Mechanical energy is only conserved in a closed system Initial (total kinetic + potential energy) = final (total kinetic + potential energy)

16. Conservation of momentum Momentum is conserved when there is no external forces E.g. snooker, assuming no friction Application? Momentum can be transferred in a collision Application?

17. Conservation of Momentum If m 1 = m 2 , then v 1 = v 2 http://www.phys.washington.edu/~young

18. Moments Turning effect of a force Moment = force x perpendicular distance Also called torque