2) Speed and Velocity.notebook

1

February 20, 2019

SPH3U Kinematics: Speed and Velocity

Lesson Goal: Just like the

last one, but with speed and

velocity!

Uniform motion is when an object travels at a constant velocity or speed. (The direction must also remain constant).

If a car travels 200 m in 10 s, its average speed is 20 m/s.

The average speed is the distance travelled divided by the elapsed time. (Unit = m/s)

v = ΔdΔt

Note: Δd can be distance OR displacement!

If distance is used, the result is speed.

If displacement is used - velocity.

One method to differentiate between a scalar and a vector is to draw an arrow over top of the variables, but it's not always adhered to. The main thing is to remember a direction for vectors.

2) Speed and Velocity.notebook

2

February 20, 2019

Negative values: Average velocity is a vector that points in the same direction as the displacement. A negative displacement means there must be a negative velocity.

(Usually we will incorporate directions rather than just give positive or negative answers.)Note: average is used for motions that have variations in speed or velocity. For motion that is truly uniform, the average can be omitted, yet understood to be stated.

2) Speed and Velocity.notebook

3

February 20, 2019

Examples1) How far does a jogger run in 1.5 h, if his average speed is 2.22 m/s?

2) How long will it take a falcon to dive 150m if the average speed of the falcon is 67m/s?

1.2 x 104 m

2.2s

3) A world record of 283 m/s for a jet-powered car was set in 1983 by Richard Noble. The driver made two runs through a measured course in each direction to account for wind effects. He travelled 604 m (left to right) in 2.12 s and travelled the same distance (right to left) in 2.15 s. Find the average velocity for each case.

285 m/s, - 281 m/s

2) Speed and Velocity.notebook

4

February 20, 2019

4) A car travels with uniform motion from a position of 2.0 km [N] to a position of 20. km [S] in 0.50 h. Find the car‛s:

a) displacement, b) velocity, c) distance, d) speed.

22 km [S], 44 km/h [S], 22 km, 44 km/h

5) A car travels 1.0 km through a town at 50.0 km/h and then drives 1.0 km through the country at 100.0 km/h. What is the average speed of this car?

67 km/h

2) Speed and Velocity.notebook

5

February 20, 2019

Instantaneous VelocitySuppose the magnitude of your average velocity was 20 m/s. This does not indicate any information about how you travelled during that time interval; perhaps you sped up to pass a car, spent time at a lower velocity as you got stuck behind a bus, etc.

The instantaneous velocity indicates the velocity at a specific point in time. The magnitude of the instantaneous velocity is the instantaneous speed.

Speed Velocity WS

Text work from Text sheet

2) Speed and Velocity.notebook

6

February 20, 2019