Velocity and Acceleration

1. Velocity and Acceleration

3. Velocity and Speed • Velocity and speed are both how fast you are going, but velocity implies a direction (N, S, E, W) as well • Four different types of speed • Instantaneous speed – how fast you are going at a certain point or time. • example: radar gun • Average speed – looks at the average speed between two points or times. • example: driving from Olympia to Seattle • Constant speed – speed stays the same • example: cruise control • Terminal velocity(speed) – the speed at which an object will stop accelerating when dropped • example: a sky-diver

4. Math for Velocity/Speed v = d/torv = d ÷ t v = velocity d = distance t = time

5. 5-Step Method to Solving Word Problems • Identify what you know (given) • Write down the correct formula to use • Show your work (“plug and chug” using calculator) • Write down answer • Make sure answer has a unit of measurement

6. Example problem • A bike travels 70 meters in 6.5 seconds. Calculate its velocity. • A car travels a distance of 100 miles in 2 hours. Calculate its velocity. Given formula show work answer w/ units d=70m v=d/t t=6.5sec 70m/6.5sec. 10.8 m/sec d=100 miles v=d/t t=2 hours 100miles/2hours 50 miles/hour

8. Acceleration • a change in velocity (speed or direction) • speeding up or slowing down • changing direction • moving in a circle is always changing direction • if acceleration is a negative number it is referred to as negative acceleration or deceleration

9. Math for Acceleration a = vf – vi t a = acceleration vf = velocity final (speed at the end) vi = velocity initial (speed at the beginning) t = time

10. Example problem • A car has an initial velocity of 3.4 m/s. After 3 seconds, its final velocity is 8.2 m/s. Calculate its acceleration. Given formula show work answer w/ units vi = 3.4m/s a = vf - vi vf = 8.2m/s t t = 3 sec. 8.2m/s – 3.4m/s 3 sec 1.6 m/s sec