1. Do now! www.mrsimonporter.wikispaces.com
Can you write in your planners that you will be having a TEST on everything we’ve done so far on Friday 1st October.
Bunny suicide #2

2. This lesson Know what a force is Types of force Vectors and scalars
Newton’s Laws

3. Forces
Remember a force is a push (or pull)

4. Forces
Force is measured in Newtons

5. Forces
There are many types of forces; electrostatic, magnetic, upthrust, friction, gravitational………

6. Friction opposes motion!

7. Newton’s Laws of Motion
That’s me!

8. Newton’s 1st Law
If there is no resultant force acting on an object, it will move with constant velocity. (Note the constant velocity could be zero).

9. Newton’s 1st Law
Does this make sense?
If there is no resultant force acting on an object, it will move with constant velocity. (Note the constant velocity could be zero).

10. Can you copy it whilst you think about it?
Newton’s 1st Law
Can you copy it whilst you think about it?
If there is no resultant force acting on an object, it will move with constant velocity. (Note the constant velocity could be zero).

11. Newton’s 1st law Newton nicked it!
Newton’s first law was actually discovered by Galileo.
Newton nicked it!

12. Newton’s first law
Galileo imagined a marble rolling in a very smooth (i.e. no friction) bowl.

13. Newton’s first law
If you let go of the ball, it always rolls up the opposite side until it reaches its original height (this actually comes from the conservation of energy).

14. Newton’s first law
No matter how long the bowl, this always happens

15. Newton’s first law No matter how long the bowl, this always happens.
constant velocity

16. Newton’s first law
Galileo imagined an infinitely long bowl where the ball never reaches the other side!

17. Newton’s first law
The ball travels with constant velocity until its reaches the other side (which it never does!).
Galileo realised that this was the natural state of objects when no (resultant ) forces act.
constant velocity

18. Another example
Imagine Mr Porter cycling at constant velocity.

19. Newton’s 1st law
He is providing a pushing force.
Constant velocity

20. Newton’s 1st law There is an equal and opposite friction force.
Pushing force
friction
Constant velocity

21. Let’s watch a video....

22. I thought of this law myself!
Newton’s second law
Newton’s second law concerns examples where there is a resultant force.
I thought of this law myself!

23. Let’s go back to Mr Porter on his bike.
Remember when the forces are balanced (no resultant force) he travels at constant velocity.
Pushing force
friction
Constant velocity

24. Newton’s 2nd law Now lets imagine what happens if he pedals faster.
Pushing force
friction

25. Newton’s 2nd law His velocity changes (goes faster). He accelerates!
Remember that acceleration is rate of change of velocity. In other words
acceleration = (change in velocity)/time
Pushing force
friction
acceleration

26. Newton’s 2nd law Now imagine what happens if he stops pedalling.
friction

27. Newton’s 2nd law
He slows down (decellerates). This is a negative acceleration.
friction

28. Newton’s 2nd law
So when there is a resultant force, an object accelerates (changes velocity)
Mr Porter’s Porche
Pushing force
friction

29. It’s physics, there’s always a mathematical relationship!
Newton’s 2nd law
There is a mathematical relationship between the resultant force and acceleration.
Resultant force (N) = mass (kg) x acceleration (m/s2)
It’s physics, there’s always a mathematical relationship!
FR = ma

30. Newton’s 2nd law
There is a mathematical relationship between the resultant force and acceleration.
Resultant force (N) = mass (kg) x acceleration (m/s2)
Can you copy this too?
FR = ma

31. An example What will be Mr Porter’s acceleration?
Mass of Mr Porter and bike = 100 kg
Pushing force (100 N)
Friction (60 N)

32. An example Resultant force = 100 – 60 = 40 N FR = ma 40 = 100a
a = 0.4 m/s2
Mass of Mr Porter and bike = 100 kg
Pushing force (100 N)
Friction (60 N)

33. Let’s watch a video...

34. Newton’s 3rd law
If a body A exerts a force on body B, body B will exert an equal but opposite force on body A.
Hand (body A) exerts force on table (body B)
Table (body B) exerts force on hand (body A)

35. Let’s watch a video...

36. Don’t worry!
We won’t really do Newton’s 3rd law until year 12!

37. That’s all folks!

38. Let’s try some questions!
He promised us it would stop…..