1. Stopping distance Write down the units for: Distance Velocity
Acceleration
Time
What is Breaking distance?
What is stopping distance?
There are 24 physics lessons left until your first exam

2. Today’s lesson Identify Two safety Features Shown on The car
Stopping distances

3. Stopping distances
stopping distance: The distance a car takes to stop.

4. Two parts
The stopping distance can be thought of in two parts

5. Stopping distances
Thinking distance: is the distance traveled whilst the driver is thinking (related to the driver’s reaction time).

6. Braking distance
Breaking distance: The distance traveled by the car once the brakes have been applied.

7. Thinking distance
Affected by:
Drink / Drugs
Tiredness
Distractions

8. Braking distance
This affected by the speed and mass of the car

9. Braking distance It is also affected by the road conditions
Wet or icy.

10. Braking distance
And by the condition of the car’s bald tyres. Or faulty brakes

11. Typical Stopping distances https://www. youtube. com/watch
Typical Stopping distances YouTube - Think! - Slow Down (Extended) (UK)

12. Breaking distance test.
Scary airplane landings- University explanation on stopping distance – Top Gear- Stopping distance:

13. Questions page 107

14. Answers 1. The distance a car travels under the breaking force
B) The distance the car travels during the drivers reaction time.
Q2 Thinkinh: tiredness, alcohol, speed, drugs
Q3 Total will increase
Q4 Friction reduced so longer to stop
Q5 Doesn’t notice the hazard until too late

15. A reminder
Energy cannot be made or destroyed, only transformed (changed).
Energy is measured in Joules.
That’s me!

16. Work
In physics, work has a special meaning, different to “normal” English.

17. Work
In physics, work is the amount of energy transformed (changed) when a force moves (in the direction of the force)

18. Important
The force has to be in the direction of movement. Carrying the shopping home is not work in physics!

19. Can you copy it down please?
Work
In physics, work is the amount of energy transformed (changed) when a force moves (in the direction of the force)

20. Work
For example, if Mr Physics pushes a table, he is doing work against the friction force of the table against the floor.

21. Calculating work
The amount of work done (measured in Joules) is equal to the force used (Newtons) multiplied by the distance the force has moved (metres).
Force (N)
Distance travelled (m)

22. Work done = Force x Distance
Can you add the units?

23. Work done(J) = Force(N) x Distance(m)
Did you get it right? Learn your units

24. Work done (J) = Force (N) x distance (m)
A woman pushes a car with a force of 400 N for a distance of 15m. How much work has she done?

25. Work done (J) = Force (N) x distance (m)
A woman pushes a car with a force of 400 N for a distance of 15m. How much work has she done?
Work = force x distance = 400 x 15 = 6000 J

26. Lifting objects
When we lift objects, we are doing work because a force is moving.
Force
Distance moved

27. Lifting objects
Our lifting force is equal to the weight of the object.
Weight= mass x gravity
Gravity = 10N/kg
Lifting force
weight

28. Work done (J) = Force (N) x distance (m)
A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do?

29. Work done (J) = Force (N) x distance (m)
A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do?
Force = weight = 1200N
Work = F x d = 1200 x 2.5
Work = 3000 J

30. Power!

31. Can you copy it down please?
Power!
Power is the amount of energy transformed (changed) per second. It is measured in Watts (1 Watt = 1 J/s)
Power = Energy transformed (work)
time
Can you copy it down please?

32. Let’s see if this dog floats!
Let’s do some more work!
Let’s see if this dog floats!
Pull!
ALL questions on page

33. Answers Q1 a) Work done=energy transferred B) D=Work/force=50/250=0.2m
Q2 To push your bike you need to push to overcome the resistant forces like friction
Q3 a T b F c T d T e F
Q4 a E=mgh=25x10x2.5=75J
B e = 28 x 300J = 8400J
Q5 d=work/force = 80000/50N = 1600m
B I force = w/d = 90000/120 = 750N
Ii W = GPE = mgh so mass = GPE/gh = 75kg