13/04/23

Speeding UpSpeeding Up

W Richards

Worthing High School

13/04/23Distance, Distance, Speed and Speed and

TimeTimeSpeed = 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?

13/04/23Balanced and unbalanced Balanced and unbalanced forcesforces

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.

13/04/23Balanced and unbalanced Balanced and unbalanced forcesforces

What would happen if we took the road away?

Weight

Reaction

13/04/23Balanced and unbalanced Balanced and unbalanced forcesforces

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

13/04/23

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 Balanced and unbalanced forcesforces

13/04/23Balanced and unbalanced Balanced and unbalanced forcesforces

13/04/23

Facts on Air ResistanceFacts on Air ResistanceAir 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

13/04/23Terminal Terminal VelocityVelocity

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

13/04/23Terminal Terminal VelocityVelocity

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

13/04/23Velocity-time graph for terminal Velocity-time graph for terminal velocity…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