1. #13 Speed and Momentum

2. Speed Depends on Distance and Time speed – the rate at which an object moves speed depends on the distance traveled and the time it takes to get there. Average speed =total distance total time

3. The speed of a bicycle is the distance it travels divided by the time it takes.

4. TS D S = D T D = S T T = D S

5. V = speed in the following equations

6. Constant Speed Speed that does not change

7. Velocity Speed with direction –A vector quantity [magnitude & direction]

8. A plane with a constant velocity of 600 km/h west moves in a straight line. (Its speed and direction remain the same.) A car going around a bend at a constant 30 mph has a constant speed, but its velocity is not constant. (Note the change in direction.)

9. Acceleration A change in velocity –Speeding up Positive acceleration –Slowing down Negative acceleration Deceleration

10. Example of Acceleration: How velocity changed: A plane taking off Increase in speed Car stopping at a light Decrease in speed (deceleration) Walking around Change in direction a corner A Ferris wheel Change In direction Acceleration = any change in speed OR direction!

11. Momentum What is momentum? The San Diego Chargers have momentum entering the final weeks of the season… Anything that is moving has momentum Depends on what?

12. Momentum The momentum of an object: -Depends on the object’s mass. Mass is the amount of matter in an object and - Depends on the object’s velocity. Velocity is speed in a given direction

13. Calculating Momentum Momentum = mass x velocity In symbols: p = mv Common units of momentum: kgm/s p m v

14. Determine the momentum of a... A) 60-kg person moving eastward at 9 m/s. p = m v p = 60 kg x 9 m/s = 540 kg·m/s east B) 1000-kg car moving northward at 20 m/s. p = m v p = 1000 kg x 20 m/s = 20,000 kg·m/s C) 40-kg dog moving southward at 2 m/s. p = m v p = 40 kg x 2 m/s = 80 kg·m/s –Which has the most momentum?