SME
Grade 10 Science · Problem type
Converting a rate
Use this to change a speed in kilometers per hour to meters per second.
Diagram
Struck through: km, h, each on a top and a bottom, so they cancel.
The unit left is m/s.
Each factor is 1 (its top and bottom are the same amount), so the amount does not change.
This is an example. Type your own values to start a new problem.
v
km/h
×
1,000
m
1
km
×
1
h
3,600
s
=
w
m/s
Formulas
w
=
v
×
1000
3600
25
=
90
×
1000
3600
Assumptions
•
1 km = 1000 m and 1 h = 3600 s exactly.
•
The hour is on the bottom of the rate, so its factor puts hours on top.
Step-by-step
WE KNOW
v = 90 km/h
FIND
speed in meters per second (w)
Step 1 · Find speed in meters per second (w)
Use w = v × 1000/3600
Multiply by 1000 m per km and by 1 h per 3600 s: km and h cancel.
w
=
90
×
1000
3600
w
=
25
m/s
Check
Put the numbers back in. Both sides should match.
25
=
90
×
1000
3600
✓
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Related lessons
Measurement, significant figures and dimensional analysis
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