Can you Sky-dive?

• This is a classic GCSE question which gets you loads of lovely points

• What do points mean?

• POINTS MEAN PASSES!

Just after Jumping Out

• The skydiver is moving slowly at first

• Air Resistance is small

• The Weight is bigger than the Air Resistance

• She ACCELERATES

Air Resistance

Weight of skydiver

After a few seconds ...

• The skydiver is moving faster now

• Air Resistance is bigger

• The Weight is still bigger than the Air Resistance

• She still ACCELERATES but at a smaller rate

Air Resistance

Weight of skydiver

After falling some time ...• The skydiver is

moving very fast now, about 60m/s

• Air Resistance is as big as the weight, but upwards.

• The Weight and Air Resistance BALANCE OUT

• She travels at a CONSTANT SPEED

Air Resistance

Weight of skydiver

Terminal Velocity(top speed)

• Remember she travels at her TERMINAL VELOCITY when

• the Weight and Air Resistance BALANCE OUT

• and so she does not accelerate but continues down at a CONSTANT SPEED

Air Resistance

Weight of skydiver

She pulls the ripcord!

• She is still GOING DOWN at about 60m/s and so the Air Resistance from the parachute’s big AREA is ENORMOUS!

• Air Resistance is bigger than her Weight so

• she DECELERATESStill the same Weight

REALLY BIG Air Resistance

She slows down, decelerates

• She is still GOING DOWN, but much slower. Air Resistance is less at the slower speed

• Air Resistance is still bigger than her Weight so

• she still DECELERATES but at a lower rate

Still the same Weight

Slower speed so less Air Resistance

Eventually ...• She is still GOING

DOWN, but quite slowly, about 12 m/s. Air Resistance is now equal to her Weight again

• Since Air Resistance now BALANCES OUT her Weight she does not accelerate

• she continues at a CONSTANT SPEED Still the

same Weight

Slower speed so less Air Resistance

Summary• Weight bigger than Air

Resistance. She ACCELERATES

• Faster speed means BIGGER Air Resistance

• When Weight and Air Resistance BALANCE OUT then she goes at constant speed or her TERMINAL VELOCITY!