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1. 23/09/15
Speeding UpSpeeding Up

2. 23/09/15
Distance, SpeedDistance, Speed
and Timeand Time
Speed = distance (in metres)
time (in seconds)
D
TS
1) Dave walks 200 metres in 40 seconds. What is his speed?
2) Laura covers 2km in 1,000 seconds. What is her speed?
3) How long would it take to run 100 metres if you run at 10m/s?
4) Steve travels at 50m/s for 20s. How far does he go?
5) Susan drives her car at 85mph (about 40m/s). How long does it
take her to drive 20km?

3. 23/09/15
Balanced and unbalanced forcesBalanced and unbalanced forces
Consider a camel standing on a road.
What forces are acting on it?
Weight
Reaction
These two forces would be equal –
we say that they are BALANCED.
The camel doesn’t move anywhere.

4. 23/09/15
Balanced and unbalanced forcesBalanced and unbalanced forces
What would happen if we took the
road away?
Weight
Reaction

5. 23/09/15
Balanced and unbalanced forcesBalanced and unbalanced forces
What would happen if we took the
road away?
The camel’s weight is no longer
balanced by anything, so the camel
falls downwards…
Weight

6. 23/09/15
What would happen if we took the
road away?
The camel’s weight is no longer
balanced by anything, so the camel
falls downwards…
Balanced and unbalanced forcesBalanced and unbalanced forces

7. 23/09/15
Balanced and unbalanced forcesBalanced and unbalanced forces
1) This animal is either
________ or moving
with _____ _____…
4) This animal is…
2) This animal is getting
_________…
3) This animal is getting
_______….

8. 23/09/15
Balanced and unbalanced forcesBalanced and unbalanced forces

9. 23/09/15
Facts on Air ResistanceFacts on Air Resistance
Air Resistance is the force that acts
___________ anything that moves
through the ______:
It can be reduced by using a more “__________” (aerodynamic) shape:
It gets _______ when
you move faster:
Streamlining also works when
travelling through _______:
Words – water, air, larger, against, streamlined

10. 23/09/15
Terminal VelocityTerminal Velocity
Consider a skydiver:
1) 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

11. 23/09/15
Terminal VelocityTerminal Velocity
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

12. 23/09/15
Velocity-time graph for terminal velocity…Velocity-time graph for terminal velocity…
Velocity
Time
Speed
increases…
Terminal
velocity
reached…
Parachute opens –
diver slows down
New, lower terminal
velocity reached
Diver hits the ground
On the Moon