1. Speed Vs Velocity

2. What is Speed? Speed is simply how quickly distance is covered.
Average Speed is measured using the following formula:
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
Average speed =
This is expressed by:
𝑑 𝑡
v =

3. Example:
The average speed of a bullet train that travels 600 km in 2 hours is:
𝑑 𝑡
v =
600 𝑘𝑚 2 ℎ
v =
So:
v = 300 km/h
So the train is travelling at an average speed of 300 kilometres per hour. But how can this be expressed in metres per second

4. Converting to metres per second (m/s)
Convert km’s into m’s by multiplying it by 1000.
𝑑 𝑡
Using: v =
600,000
600 𝑘𝑚 2 ℎ
v =
7200
Convert hours into seconds by multiplying it by 3600.
Why? 60 seconds to a minute and 60 minutes to an hour, so 60 x 60 = 3600
So: v = m/s

5. Distance and Time
If we are looking for distance or time, we need to rearrange the formula to suit.

6. Example:
The distance covered in 3.5 hours by a sloth travelling at and average speed of 0.24 km/h is:
YAY
Distance = speed x time
So: Distance = .24 km/h x 3.5 h
So: Distance = 0.84 km

7. Velocity How is Velocity different to speed?
Instead of measuring how quickly distance is covered, Velocity measures the rate of change in position.
When measuring velocity direction is also considered.

8. Example:
A blue car travels from point A, 30 km’s to the east and then 40 km’s to the north, arriving at point B in 2 hours, its speed is as follows: B A
40 km’s North
30 km’s East
30+40 𝑘𝑚 2 ℎ
v =
So: v = 35 km/h

9. Notice the “D” rather than “d”. Refers to Displacement
Example:
However, a red car travels from point A, and drives 50 km on a direct route arriving at point B in 2 hours, its speed is as follows:
30 km’s East
40 km’s North B A
50km’s NE
Velocity = 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
Notice the “D” rather than “d”. Refers to Displacement
𝐷 𝑡
Using: v =
50 𝑘𝑚 𝑁𝐸 2 ℎ
v =
So: v = 25 km/h

10. Blue Car Red Car Average Speed Average Velocity
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
70 𝑘𝑚 2 ℎ = 35 km/h
50 𝑘𝑚 2 ℎ = 25 km/h NE
Average Velocity
𝐷𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛

11. Changing Speed Acceleration: How quickly the speed changes.
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
Average acceleration =
𝑎= ∆𝑣 𝑡

12. For example:
A greyhound racing at 43 km/h, that increased its speed to the average race speed of 63km/h in 2.5 seconds has an average acceleration of:
𝑎= ∆𝑣 𝑡 𝑎=
a = 8.0 km/h per second

13. For example 2:
A greyhound racing at the average race speed of 63 km/h, that decreased its speed to 3 km/h in 3 seconds has an average deceleration of:
𝑎= ∆𝑣 𝑡
𝑎= −60 3
a = -20 km/h per second