Åk 6–9
 
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3.2 Units for Velocity and Speed

Meters per second
1 m/s


Kilometers per hour
1 km/h



Miles per hour
Used mostly in the USA and England.

1 mph = 1.609 km/h = 0.4469 m/s


Foto: Fredrik Enander





Knots
Used mostly in nautical situations.

1 knot = 0.5144 m/s = 1.852 km/h

Photo: Max Krabbenhöft




Mach 1
The speed of sound in air at sea level.

1 Mach = 343 m/s = 1234.8 km/h





How many kilometers per hour is 1 meter per second?
1 min = 60 s

1 h = 60 min = (60 · 60) s = 3,600 s

3,600 m/h = 3.6 km/h

1 m/s = 3.6 km/h

How many meters per second is 1 kilometer per hour?
1 km/h = 1,000 m/h ≈ 1,000/60 ≈ 16.7 m/min ≈ 0.28 m/s

1 km/h ≈ 0.28 m/s




Calculation Example

Example A
What is the velocity 5 m/s expressed in km/h?

5 m/s = 5 · 60 m/min = 300 m/min
300 m/min = 300 · 60 m/h = 18,000 m/h
18,000 m/h = 18 km/h

Answer: 18 km/h

Example B
What is the velocity 108 km/h expressed in m/s?

108 km/h = 108,000 m/h
108,000/60 m/min = 1,800 m/min
1,800/60 m/s = 30 m/s

Answer: 30 m/s