L4 - Speed

L4 - Speed

Speed

LO: Understanding the concept of speed

• Must - Define speed

• Should - Calculate average speed from (total distance)/(total time)

Speed is a measure of how fast an object is moving. 

• Speed can be calculated using the equation: 

•  $speed\ =\ \frac{dis\tan ce}{time}$  

Open Ended

Answer the following questions:

1)Ben walks 200 metres in 40 seconds. What is his speed?

2)Andy covers 2 km in 1,000 seconds. What is his speed?

3)How long would it take Connor to run 100 metres if he could run at 12 m/s?

4)Dan throws a book at Adam and it travels at 50 m/s for 0.2s. How far away was Adam?

(Check your answers in the next slide)

• 1) speed =  $\frac{200}{40}$  = 5 m/s

• 2) speed =  $\frac{2000\ m}{1000\ s}$  = 2 m/s

• 3) time =  $\frac{100}{12}$  = 8.33 s

• 4) distance =  $50\times0.2$  = 10 m

Average Speed

• The speed of an object usually changes over time. That is, it does not have a constant speed throughout the journey.

• For example: Your commute to school this morning.

• We can calculate the average speed as:  $\frac{total\ dis\tan ce}{total\ time}$  

Open Ended

A trucks journey is broken down into 4 different segments, and is recorded in the table.

Determine the:

a)Total distance traveled

b)Total time taken

c)Average speed of the entire journey

(Check your answers in the next slide)

• a) total distance = (50 + 35 + 50 + 75) = 210 km
  

• b) total time= (1.5 + 1.0 + 1.5 + 2.5) = 6.5 hours

• c) average speed =  $\frac{210}{6.5}$  =32.3 km/h

Open Ended

John drove for 3 hours at a rate of 50 km/h and for 2 hours at 60 km/h. What was his average speed for the whole journey?

(Hint: The answer is NOT 55 km/h)

• Total distance =  $\left(3\times50\ +\ 2\times60\right)$  =270 km

• Total time = (3 + 2) = 5 hours

• Average speed =  $\frac{270}{5}$  =54 km/h

Speed

LO: Understanding the concept of speed

• Must - Define speed

• Should - Calculate average speed from (total distance)/(total time)