1. Forces and Motion EdExcel iGCSE 9-1 Physics topic 1 W Richards
27/01/2020
27/01/2020
Forces and Motion
EdExcel iGCSE 9-1 Physics topic 1
W Richards
Education Using PowerPoint

2. Movement and Position
27/01/2020

3. Distance, Speed and Time
27/01/2020
27/01/2020
Distance, Speed and Time s t v
Speed = distance (in metres)
time (in seconds)
You are expected to learn this equation!!!
Will walks 200 metres in 40 seconds. What is his speed?
Ruby covers 2km in 1,000 seconds. What is her speed?
How long would it take Sophie to run 100 metres if she runs at 10m/s?
Aaron runs to the shop to buy Fifa 19 and travels at 50m/s for 20s. How far does he go?
Taylor drives her car at 85mph (about 40m/s). How long does it take her to drive 20km?
5m/s
2m/s
10s
1000m
500s

4. Distance, Speed and Time (harder)
27/01/2020
27/01/2020
Distance, Speed and Time (harder) s t v
Speed = distance (in metres)
time (in seconds)
Eliza walks 2000m in 50 minutes. What is her speed in m/s?
Archie tries to walk the same distance at a speed of 5m/s. How long does he take?
David drives at 60mph (about 100km/h) for 3 hours. How far has he gone?
The speed of sound in air is 330m/s. Isobel shouts at a mountain and hears the echo 3 seconds later. How far away is the mountain? (Careful!)
0.67m/s
400s
300km
495m

5. What about cars? Aeroplanes?
Speed
27/01/2020
What are the typical speeds for when you walk, run and ride a bike?
Walking ≈ 1.5m/s
Running ≈ 3m/s
Cycling ≈ 6m/s
What about cars? Aeroplanes?

6. Distance-time graphs 2) Horizontal line = 40 30 20 10
27/01/2020
27/01/2020
2) Horizontal line = 40 30 20 10
4) Diagonal line downwards =
Distance
(metres)
3) Steeper diagonal line =
Time/s
Diagonal line =

7. 40 30 20 10 20 40 60 80 100 0.5m/s 40m 1m/s 40-60s Distance (metres)
27/01/2020
27/01/2020
Distance
(metres)
Time/s
What is the speed during the first 20 seconds?
How far is the object from the start after 60 seconds?
What is the speed during the last 40 seconds?
When was the object travelling the fastest?
0.5m/s
40m
1m/s
40-60s

8. Who was travelling the fastest? 40 30 20 10
27/01/2020 N G B
Distance
(metres)
Time/s Y
Who was travelling the fastest?
Who was travelling the slowest (but still moving)?
Who didn’t move?

9. Task: Produce a distance-time graph for the following journey:
Distance-Time graphs
27/01/2020
Task: Produce a distance-time graph for the following journey:
Christina walks 50m in 20 seconds.
She then stands still for 10 seconds
She then runs away from Luke and covers 100m in 30 seconds.
She then stands still and catches her breath for 20 seconds.
She then walks back to the start and covers the total 150m in 50 seconds.

10. 40 30 20 10 20 40 60 80 100 1.5m/s 0.5m/s 1m/s Distance (metres)
27/01/2020
27/01/2020
Distance
(metres)
Time/s
What was the velocity in the first 20 seconds?
What was the velocity between 20 and 40 seconds?
When was this person travelling the fastest?
What was the average speed for the first 40 seconds?
1.5m/s
0.5m/s
80-100s
1m/s

11. 40 30 20 10 20 40 60 80 100 2m/s 35m 0.25m/s 20-40s Distance (metres)
27/01/2020
27/01/2020
Distance
(metres)
Time/s
What is the speed during the first 20 seconds?
How far is the object from the start after 50 seconds?
What is the speed during the last 40 seconds?
When was the object standing still?
2m/s
35m
0.25m/s
20-40s

12. You need to learn this equation!!
Acceleration
27/01/2020
27/01/2020
V-U T A
Acceleration = change in speed (in m/s)
(in m/s2) time taken (in s)
You need to learn this equation!!
A cyclist accelerates from 0 to 10m/s in 5 seconds. What is her acceleration?
A ball is dropped and accelerates downwards at a rate of 10m/s2 for 5 seconds. How fast will it be going?
A car accelerates from 0 to 20m/s with an acceleration of 2m/s2. How long did this take?
A rocket accelerates from 0m/s to 5,000m/s in 2 seconds. What is its acceleration?
2m/s2
50m/s
10s
2500m/s2

13. Acceleration (harder)
27/01/2020
27/01/2020
Acceleration (harder)
V-U T A
Acceleration = change in velocity (in m/s)
(in m/s2) time taken (in s)
A cyclist slows down from 10 to 0m/s in 5 seconds. What is her acceleration?
A ball is dropped and accelerates downwards at a rate of 10m/s2 for 12 seconds. How much will the ball’s velocity change by?
A car accelerates from 10 to 20m/s with an acceleration of 2m/s2. How long did this take?
A rocket accelerates from 1,000m/s to 5,000m/s in 2 seconds. What is its acceleration?
-2m/s2
120m/s 5s
2000m/s2

14. Velocity-time graphs 1) Upwards line = 80 60 40 20 4) Downward line =
27/01/2020
27/01/2020
1) Upwards line = 80 60 40 20
4) Downward line =
3) Upwards line =
Velocity
m/s
2) Horizontal line =
T/s

15. How fast was the object going after 10 seconds? 80 60 40 20
27/01/2020
27/01/2020
Velocity
m/s
T/s
How fast was the object going after 10 seconds?
What is the acceleration from 20 to 30 seconds?
What was the deceleration from 30 to 50s?
How far did the object travel altogether?
40m/s
2m/s2
3m/s2
1700m

16. How fast was the object going after 10 seconds? 80 60 40 20
27/01/2020
27/01/2020
Velocity
m/s
T/s
How fast was the object going after 10 seconds?
What is the acceleration from 20 to 30 seconds?
What was the deceleration from 40 to 50s?
How far did the object travel altogether?
10m/s
4m/s2
6m/s2
1500m

17. 80 60 40 20
27/01/2020
27/01/2020
Velocity
m/s
T/s
David runs home to tell someone about his commendation. This velocity-time graph shows David’s journey to home. How far away does he live?
2500m

18. Acceleration (recap) V-U T A
27/01/2020
27/01/2020
Acceleration (recap)
V-U T A
Acceleration = change in velocity (in m/s)
(in m/s2) time taken (in s)
Eliza accelerates from standstill to 50m/s in 25 seconds. What is her acceleration?
Hayden accelerates at 5m/s2 for 5 seconds. He started at 10m/s. What is his new speed?
Luke is in trouble with the police. He is driving up the A29 and sees a police car and brakes from 50m/s to a standstill. His deceleration was 10m/s2. How long did he brake for?
Archie brakes at the same deceleration but only for 3 seconds. What speed did he slow down to?
2m/s2
35m/s 5s
20m/s

19. 80 60 40 20
27/01/2020
27/01/2020
Velocity
m/s
T/s
This velocity-time graph shows Sonny’s journey to school. How far away does he live?
2200m

20. Another equation of motion
27/01/2020
For a constantly-accelerating body, we can also use this equation:
You DON’T need to learn this equation!!
v2 = u2 + 2as
An object starts from rest and accelerates at a rate of 2m/s2 over a distance of 20m. What is its final velocity?
Aaron drives up the M1 and covers 30km. He started at 2m/s and constantly accelerated during the whole journey at a rate of 0.001m/s2. What was his final speed?
(Harder!) Rachael decelerates from 30 to 10m/s over a distance of 5m. What is her acceleration?
8.9m/s
8m/s
-80m/s2

21. Calculating acceleration using Ticker Tape
27/01/2020
Find the first “distinct” dot and draw a line through it:
2) Count 5 gaps (=5/50ths or 1/10th of a second) and draw another line:
3) Repeat for every tenth of a second:
4) Cut the strips out and stick them next to each other onto graph paper:

22. Calculating acceleration using Ticker Tape
27/01/2020
Your graphs will look like this:
To calculate the acceleration you need to follow 3 easy steps:
Work out the START and END speeds:
Start speed = 1cm/0.1s = 10cm/s
End speed = 5cm/0.1s = 50cm/s
Work out the time taken:
Time taken = = 0.4s
V-U T A
Calculate the acceleration:
A = (50 – 10) / 0.4 = 100cm/s2

23. Forces, Movement, Shape and Momentum
27/01/2020
Forces, Movement, Shape and Momentum

24. The Effect of Forces
27/01/2020
What are forces doing in each of the following situations?

25. What is a force? Words – upthrust, air resistance, friction, weight
27/01/2020
Forces are usually gravitational or electrostatic. Some examples:
___ ________ (drag) – acts against anything moving through air (electrostatic)
________ – pulls things downwards (gravitational)
_____ – acts against anything moving (electrostatic)
______ – keeps things afloat (electrostatic)
Words – upthrust, air resistance, friction, weight

26. Speed vs. Velocity Speed is simply how fast you are travelling…
27/01/2020
27/01/2020
Speed is simply how fast you are travelling…
This car is travelling at a speed of 20m/s
Velocity is “speed in a given direction”…
This car is travelling at a velocity of 20m/s east

27. Circular Motion 1) Is this car travelling at constant speed?
27/01/2020
27/01/2020
1) Is this car travelling at constant speed?
2) Is this car travelling at constant velocity?

28. Vector vs. scalar
27/01/2020
Scalar quantities have size (“magnitude”) only and no direction.
Vector quantities have both size and direction.
Scalar or vector???
Scalar
Vector
8. Power
2. Distance
1. Mass
6. Energy
7. Time
3. Acceleration
4. Speed
9. Force
5. Velocity

29. Balanced and unbalanced forces
27/01/2020
27/01/2020
Reaction
Consider a camel standing on a road. What forces are acting on it?
These two forces would be equal – we say that they are BALANCED. The camel doesn’t move anywhere.
Weight

30. Balanced and unbalanced forces
27/01/2020
27/01/2020
Reaction
What would happen if we took the road away?
There is a “resultant force” which causes the camel to accelerate downwards (the same direction as the force).
Weight

31. Balanced and unbalanced forces
27/01/2020
27/01/2020
Predict what these cars will do and explain why:

32. Balanced and unbalanced forces
27/01/2020
27/01/2020
1) This animal is either ________ or moving with _______ _____…
2) This animal is getting ________…
3) This animal is getting _______….
4) This animal is also either _______ or moving with ________ ______..
Words - Stationary, faster, slower or constant speed?

33. Summary Complete these sentences…
27/01/2020
27/01/2020
Complete these sentences…
If an object is stationary and has NO resultant force on it the object will…
If an object is stationary and a resultant force acts on it the object will…
If an object is already moving and NO resultant force acts on it the object will…
If an object is already moving and a resultant force acts on it the object will…
…accelerate in the direction of the resultant force
…continue to move at the same speed and the same direction
…continue to stay stationary
…accelerate in the direction of the resultant force

34. Resultant Force
27/01/2020
27/01/2020
A “resultant force” is a single force that can replace all of the other forces acting on something. Calculate and draw the resultant force of the following:
700N
600N
500N
100N
50N
700N
700N
800N
800N
200N
100N

35. Force and acceleration
27/01/2020
27/01/2020
If the forces acting on an object are unbalanced then the object will accelerate, like these wrestlers:
Force (in N) = Mass (in kg) x Acceleration (in m/s2)
You need to learn this equation!! F A M

36. Force, mass and acceleration
27/01/2020
27/01/2020
A force of 1000N is applied to push a mass of 500kg. How quickly does it accelerate?
A force of 3000N acts on a car to make it accelerate by 1.5m/s2. How heavy is the car?
A car accelerates at a rate of 5m/s2. If it weighs 500kg how much driving force is the engine applying?
A force of 10N is applied by a boy while lifting a 20kg mass. How much does it accelerate by? F A M
2m/s2
2000kg
2500N
0.5m/s2

37. You need to learn this equation!!
Weight vs. Mass
27/01/2020
27/01/2020
Earth’s Gravitational Field Strength is 10N/kg. In other words, a 1kg mass is pulled downwards by a force of 10N. W g M
Weight = Mass x Gravitational Field Strength
(in N) (in kg) (in N/kg)
You need to learn this equation!!
What is the weight on Earth of a book with mass 2kg?
What is the weight on Earth of an apple with mass 100g?
David weighs 700N on the Earth. What is his mass?
On the moon the gravitational field strength is 1.6N/kg. What will David weigh if he stands on the moon?
20N 1N
70kg
112N

38. Stopping a car…
27/01/2020
27/01/2020
What two things must the driver of the car do in order to stop in time?

39. Stopping a car… Braking distance Thinking distance (reaction time)
27/01/2020
27/01/2020
Thinking distance
(reaction time)
Braking distance

40. Total Stopping Distance = Thinking Distance + Braking Distance
Stopping a car…
27/01/2020
27/01/2020
Tiredness
Too much alcohol
Thinking distance
(reaction time)
Too many drugs
Poor visibility
Wet roads
Icy roads
Braking distance
Tyres/brakes worn out
Driving too fast
Total Stopping Distance = Thinking Distance + Braking Distance

41. Stopping Distances
27/01/2020

42. Terminal Velocity Consider a ball falling through a liquid:
27/01/2020
Consider a ball falling through a liquid:
Some questions to consider:
1) What forces are acting on the ball?
2) How do those forces change when the ball gets faster?
3) Will the ball keep getting faster? Explain your answer in terms of forces

43. Words – increase, small, constant, balance, accelerates
Terminal Velocity
27/01/2020
27/01/2020
Consider a skydiver:
At the start of his jump the air resistance is _______ so he _______ downwards.
2) As his speed increases his air resistance will _______
3) Eventually the air resistance will be big enough to _______ the skydiver’s weight. At this point the forces are balanced so his speed becomes ________ - this is called TERMINAL VELOCITY
Words – increase, small, constant, balance, accelerates

44. Words – slowing down, decrease, increases, terminal velocity, weight
27/01/2020
27/01/2020
Consider a skydiver:
4) When he opens his parachute the air resistance suddenly ________, causing him to start _____ ____.
5) Because he is slowing down his air resistance will _______ again until it balances his _________. The skydiver has now reached a new, lower ________ _______.
Words – slowing down, decrease, increases, terminal velocity, weight

45. Velocity-time graph for terminal velocity
27/01/2020
27/01/2020
Velocity
Parachute opens – diver slows down
Speed increases…
Terminal velocity reached…
On the Moon
Diver hits the ground
New, lower terminal velocity reached
Time

46. Force and Extension Consider a mass on a spring:
27/01/2020
Consider a mass on a spring:
What happens when a mass is added?
When a force is applied to this spring it will change shape and extend.

47. Investigating Force and Extension
27/01/2020
Task: Find an expression that relates extension to the amount of weight added.
Weight added (N)
Extension (cm) 1 2 3 4 5 6
Force is proportional to extension – “Hooke’s Law”

48. Force-Extension Graph for a spring
27/01/2020
Force/N
Extension/mm
The “limit of proportionality”.
Force is proportional to extension as long as you don’t go past the “limit of proportionality”. There is a linear relationship up to here – the object has obeyed Hooke’s Law up to this point.

49. Elastic and Inelastic Deformation
27/01/2020
Force/N
Extension/mm
If you don’t use too much force on the spring you can take the force off and the spring returns to its original shape – this is “elastic deformation”.
If you put too much force on the spring it “stretches” – in other words, when you remove the force the spring does not go back to its original length. This is “inelastic deformation”.

50. Force-Extension Graph for a wire
27/01/2020
Force/N
Extension/mm
The “elastic limit”
The “plastic region”
The “limit of proportionality”
“Permanent deformation”

51. Force-Extension Graph for rubber
27/01/2020
Force/N
Extension/mm

52. You need to learn this equation!!
Momentum
27/01/2020
27/01/2020
Any object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula: P V M
Momentum = Mass x Velocity
(in kgm/s) (in kg) (in m/s)
You need to learn this equation!!
What is the momentum of the following?
Archie (mass 50kg) running at 10m/s
A 1000kg car travelling at 30m/s
A 0.02kg pen thrown across the room at 5m/s
Mr Richards (mass 90kg) bungee jumping and falling at 40m/s
500kgm/s
30,000kgm/s
0.1kgm/s
3600kgm/s

53. Conservation of Momentum
27/01/2020
27/01/2020
In any collision or explosion momentum is conserved (provided that there are no external forces have an effect). Example question:
Two cars are racing around the M25. Car A collides with the back of car B and the cars stick together. What speed do they move at after the collision?
Speed = 50m/s
Speed = 20m/s
Mass = 1000kg
Mass = 800kg
Speed = ??m/s
Mass = 1800kg
Momentum before = momentum after…
…so 1000 x x 20 = 1800 x V…
…V = 36.7m/s

54. Momentum in different directions
27/01/2020
27/01/2020
What happens if the bodies are moving in opposite directions?
Speed = 50m/s
Mass = 1000kg
Speed = 20m/s
Mass = 800kg
Momentum is a VECTOR quantity, so the momentum of the second car is negative…
Total momentum = 1000 x 50 – 800 x 20 = kgm/s
Speed after collision = kgm/s / 1800 = 18.9m/s

55. More questions…
27/01/2020
27/01/2020
A car of mass 1000kg heading up the M1 at 50m/s collides with a stationary truck of mass 8000kg and sticks to it. What velocity does the wreckage move forward at?
A defender running away from a goalkeeper at 5m/s is hit in the back of his head by the goal kick. The ball stops dead and the player’s speed increases to 5.5m/s. If the ball had a mass of 500g and the player had a mass of 70kg how fast was the ball moving?
A white snooker ball moving at 5m/s strikes a red ball and pots it. Both balls have a mass of 1kg. If the white ball continued in the same direction at 2m/s what was the velocity of the red ball?
A gun has a recoil speed of 2m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g what speed does the bullet come out at?
5.6m/s
70m/s
3m/s
400m/s

56. Recap question on momentum
27/01/2020
27/01/2020
Milton and Aaron are racing against each other over 400m at Sports Day. Milton is running at 8m/s and catches up with Aaron who is running at 6m/s. After the collision Milton stops and Aaron moves slightly faster. If Milton’s mass is 60kg and Aaron’s is 70kg calculate how fast Aaron moves after the collision.
Lilian is driving her 5kg toy car around. It is travelling at 10m/s when it hits the back of Christina’s (stationary) leg and sticks to it. Assuming Christina’s leg can move freely and has a mass of 10kg calculate how fast it will move after the collision.
12.9m/s
3.3m/s

57. An extension question using standard form
27/01/2020
27/01/2020
An extension question using standard form
Consider the nuclear decay of Americium-241: α 4 2 Np
237 93 Am
241 95
If the new neptunium atom moves away at a speed of 5x105 m/s what was the speed of the alpha particle?
2.96x107 m/s

58. Change in Momentum and Force
27/01/2020
Instead of F=ma Newton actually said that the force acting on an object is that object’s rate of change of momentum. In other words…
mv-mu T F
Force = Change in momentum
Time
(in N)
(in kgm/s)
(in s)
You DON’T need to learn this equation!!
For example, Luke scores from a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:
The change in momentum of the ball (its impulse),
The speed the ball moves away with

59. Example questions
27/01/2020
Archie likes playing golf. He strikes a golf ball with a force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.
Aaron thinks it’s funny to hit tennis balls at David. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.
Ruby takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If her foot was in contact with the ball for 0.1 seconds calculate the force she applied to the ball.
Taylor strikes a 200g golf ball away at 50m/s. If she applied a force of 50N calculate how long her club was in contact with the ball for.
16kgm/s,
80m/s
4.5kgm/s,
18m/s
40N
0.2s

60. Safety features How do air bags and crumple zones work? Basically:
27/01/2020
27/01/2020
How do air bags and crumple zones work?
Basically:
The change in momentum is the same with or without an airbag
But having an airbag increases the time of the collision
Therefore the force is reduced

61. Newton’s 1st Law of Motion
27/01/2020
Basically, a body will remain at rest or continue to move with constant velocity as long as the forces acting on it are balanced.
Newton
…and an unbalanced backwards force will make me slow down…
An unbalanced forwards force will make me accelerate…

62. Newton’s 2nd Law of Motion
27/01/2020
Newton
The acceleration of a body is proportional to the resultant force causing its acceleration and is in the same direction.
In other words…
force = mass x acceleration F A M

63. Newton’s 3rd Law of Motion
27/01/2020
Newton
When body A exerts a force on body B, body B exerts an equal and opposite force on body A.
My third law says that if I push to the right I will move backwards as well.

64. Newton’s 3rd Law of Motion
27/01/2020
What will happen if I push this satellite away from me?

65. Newton’s Laws Project
27/01/2020
Task: Create a 2-3 minute presentation on Newton’s 3 Laws, to include:
A clear description of each law
A demonstration of it in action

66. Balanced or unbalanced?
27/01/2020

67. You need to learn this equation!!
Turning Moments
27/01/2020
A moment is a “turning force”, e.g. trying to open or close a door or using a spanner. The size of the moment is given by:
Moment (in Nm) = force (in N) x PERPENDICULAR distance from pivot (in m)
You need to learn this equation!!
Calculate the following turning moments:
5 metres
100 Newtons
2 metres
200 Newtons

68. Turning Moments 2 metres 2 metres
27/01/2020
2 metres
2 metres
Total ANTI-CLOCKWISE turning moment = 200x2 = 400Nm
Total CLOCKWISE turning moment = 100x2 = 200Nm
200 Newtons
100 Newtons
The anti-clockwise moment is bigger so the seesaw will turn anti-clockwise

69. An example question ? metres 5 metres 2000 Newtons 800 Newtons
27/01/2020
? metres
5 metres
2000 Newtons
800 Newtons

70. Calculate the missing quantity
27/01/2020
The following are all balanced:
??N 2N 4m 2m 5N 3N 2m
??m 5N 5N
15N 4m 2m
??m

71. A hard question…
27/01/2020
Consider a man walking along a plank of wood on a cliff.
How far can he walk over the cliff before the plank tips over?
Aaarrgghh
Man’s weight = 800N 1m
Plank’s weight = 200N 3m

72. A recap question Calculate the mass of man in the example given below:
27/01/2020
Calculate the mass of man in the example given below:
30kg
0.4m
1.2m

73. Centre of Gravity
27/01/2020
The weight of an object always acts through the object’s centre of gravity.
Where is the centre of gravity for these objects?

74. Driving along a bridge Consider a car on a suspension bridge:
27/01/2020
Consider a car on a suspension bridge:
As the car drives along the bridge, how would the upwards force on each beam change?
Upwards force = ???
Upwards force = ???

75. Extension – calculating the force
27/01/2020
To find out what the size of the force is, take moments about a pivot at the base of the supports:
20m 3m
Weight of car = 10,000N
Weight of bridge = 500,000N