Speed and velocityApril 12, 2023

Copy and complete the following table:

Quantity Symbol Unit Symbol Equation

Speed        

Distance        

Time        

Quantity Symbol Unit Symbol Equation

Speed vmetre per second

m/s v=d/t

Distance d metre m d=vt

Time t second s t=d/v

time

distancespeed

Definition

• Speed is the rate of change of distance

time

distancespeed

t

dv

221

r

mGmmg

Why I don’t like formula triangles

Now stick that in a triangle…

Can you calculate speed?

• Usain Bolt can run 100 m in 9.58 second. How fast does he run?

Worked example

1-ms OR m/s 44.10

58.9

100

?

58.9

100

v

s

mv

t

dv

v

st

md

Two types of speed

• How fast was Usain Bolt running at the start?

• How fast was he running in the middle?

• How fast was he running at the finish?

Average speed

taken timetotal

travelleddistance totalspeed average

Instantaneous speed

• This is the speed at any given moment (or instant!)

• A speedometer in a car gives the instantaneous speed but you would have to calculate the average speed (most GPS systems can do this for you)

Displacement

• The difference between the starting point and finishing point. It is distance with direction

How far does a football travel during a match?

• Distance: many kilometers

• Displacement: 0

Velocity

• The rate of change of displacement

• OR

• How fast you are going in a particular direction

Velocity

t

sv

http://upload.wikimedia.org/wikipedia/commons/f/f2/Orbit2.gif

Graphing movementApril 12, 2023

Learning objective

• Draw and interpret distance-time graphs

• Draw and interpret velocity-time graphs

Define these terms…

• Distance

• Displacement

• Speed

• Velocity

The Moving Man

To do

• Using graph paper draw a distance-time graph of your journey to school

• Now try a velocity-time graph of the same journey