1. Motion Notes 3 Forces : Terminal velocity

2. Terminal 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 zero accelerates increase balance constant

3. How the forces change with time. KEY Weight (constant value and always present) Air resistance (proportional to the speed) Resultant force (the bigger the unbalanced force the greater the acceleration)

4. Terminal 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 _______ until it balances his _________. The skydiver has now reached a new, lower ________ _______. increases slowing down decrease weight terminal velocity

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

6. Stopping = thinking + braking distance distance distance What is stopping distance? What is thinking distance? What factors will affect it? What is braking distance? What factors will affect it ? How can we work out how fast an object is travelling? Speed = total distance / time taken

7. Answers! The stopping distance is the distance the car travels from the time the driver realises that he needs to stop, to the time when the car actually stops moving. The thinking distance is the distance the car moves between the driver realising that he has to stop and when he steps on the brake. Factors that will affect thinking distance : Too much alcohol Thinking distance Tiredness Too many drugs

8. More answers! Braking distance Wet roads The speed of the car Tyres/brakes worn out Icy roads The braking distance is the distance the car moves while the brakes are being depressed.

9. Typical Stopping Distances 20 MPH 6 metres 6 metres ………….. 12 metres 30 MPH 9 metres 14 metres …………. 23 metres 40 MPH 12 metres 24 metres ……..………. 36 metres 50 MPH 15 metres 38 metres ………….... 53 metres 60 MPH 18 metres 55 metres ……..……… 73 metres