Do now!Can you copy this please?
Speed and velocity
Velocity is speed and DIRECTION. It is a vector quantity. “My velocity was 5 m/s NORTH.”
“Cool Runnings”
questions for homework.
Due Thursday 28th
September
Acceleration
speed
time
a = v – u
t
(v= final speed, u = initial speed)
v
u
Acceleration (m/s2)
acceleration = change in speed time taken
a = v – ut
a = acceleration (m/s2)v = final speed (m/s)u = initial speed (m/s)t = time taken (s)
Getting faster? (accelerating)
speed
time
The area under the graph gives the distance travelled
Do now!
• Can you make your Seed Spinners using the instructions?
Falling!
Imagine a dog being thrown out of an aeroplane.
Woof! (help!)
Force of gravity means the dog accelerates
gravityTo start, the dog is falling slowly (it has not had time to speed up).
There is really only one force acting on the dog, the force of gravity.
The dog falls faster (accelerates) due to this force.
Gravity is still bigger than air resistance
gravity
As the dog falls faster, another force becomes bigger – air resistance.
The force of gravity on the dog of course stays the same
The force of gravity is still bigger than the air resistance, so the dog continues to accelerate (get faster)
Air resistance
Gravity = air resistanceTerminal velocity
gravity
As the dog falls faster and air resistance increases, eventually the air resistance becomes as big as (equal to) the force of gravity.
The dog stops getting faster (accelerating) and falls at constant velocity.
This velocity is called the terminal velocity.
Air resistance
Gravity = air resistanceTerminal velocity
gravity
As the dog falls faster and air resistance increases, eventually the air resistance becomes as big as (equal to) the force of gravity.
The dog stops getting faster (accelerating) and falls at constant velocity.
This velocity is called the terminal velocity.
Air resistance
Terminal Velocity
The dog will continue to fall at constant speed (called the terminal speed) until………….
gravity
Air resistance
air resistance = gravity
Terminal Velocity
gravity
Air resistance
Oooooops!
That definitely was terminal!
YouTube - Moonraker Pre Credits
Can you stick the sheet in?
YouTube - Moonraker Pre Credits
Falling without air resistance
Falling without air resistance
Falling without air resistance
gravity
This time there is only one force acting in the ball - gravity
Falling without air resistance
gravity
The ball falls faster….
Falling without air resistance
gravity
The ball falls faster and faster…….
Falling without air resistance
gravity
The ball falls faster and faster and faster…….
It gets faster by 10 m/s every second (10 m/s2)
This number is called “g”, the acceleration due to gravity.
Falling without air resistance
gravity
Without air resistance objects fall faster and faster and faster…….
They get faster by 10 m/s every second (10 m/s2)
This number is called “g”, the acceleration due to gravity.
Can you copy the words please?
Where did I come from?
Falling without air resistance?
speed
time
Falling without air resistance?
speed
time
Falling without air resistance?
speed
time
Gradient = acceleration = 10 m/s2 (9.81)
Falling with air resistance?
speed
time
Falling with air resistance?
speed
time
Terminal speed
Let’s do an investigation
Investigating the terminal velocity of a
cupcake case.
Do now – copy this!
• The gradient (rise over run) of a speed/time graph gives the acceleration.
• The area under a speed/time graphs gives the distance travelled.
TEST!
• Monday 9th October• Everything we have done so far this year
(speed and speed/time graphs). • ALL LESSON POWERPOINTS are on
www.mrsimonporter.wikispaces.com• Can you also finish the sheets we have
done this lesson?
“Ticket to exit”?!