1. Speed & Velocity

2. Speed Anything that is in motion has speed. Speed is a scalar quantity—a measurement that does not include direction.

3. Speed Speed (s) = Rate at which an object is moving. speed = distance / time s = d/t Like distance, speed does not depend on direction.

4. Speed A car drives 100 meters in 5 seconds. What is the car’s average speed? – s = d/t – s = (100 m) / (5 s) = 20 m/s 100 m 1 s2 s3 s4 s5 s

5. Speed A racecar is traveling at 85.0 m/s. How far does the car travel in 30.0 s?

6. Speed Speed is the rate at which distance changes. The word rate means the ratio of how much something changes divided by how long the change takes. Constant speed means the same change in distance is traveled every second.

8. Calculating speed The change in position is a distance traveled in a given amount of time. To calculate the speed of an object, you need to know two things: – the distance traveled by the object – the time it took to travel the distance

9. 1.You are asked for speed in m/s. 2.You are given distance = 50 m; time = 7.5 s 3.Use s = d ÷ t 4.Put in values and solve. s = 50 m ÷ 7.5 s ≈ 6.67 m/s Calculating speed in meters per second  A bird is observed to fly 50 meters in 7.5 seconds. Calculate the speed of the bird in m/sec.

10. Velocity Another characteristic is needed to describe motion—direction! Velocity = displacement over time  speed in a given direction. Velocity is a vector quantity = a measurement that includes direction. velocity = displacement / time v =  d / t

11. Pulling It All Together – Distance traveled: 7 cm – Displacement: +3 cm – Average speed: (7 cm) / (5 s) = 1.4 cm/s – Average velocity: (+3 cm) / (5 s) = +0.6 cm/s cm 012345678910 + - 1 s2 s3 s4 s5 s

12. Calculating Velocity To calculate velocity, you must know two things: 1) Change in position (displacement) 2) Time during which the change took place FIND the formula on your reference sheet for calculating velocity. Units for describing velocity are the same as for describing speed but also have a direction.