The Problem:
The speed limit on a motorway is 120 km per hour. What is this in SI units?
Solution:
Step 1: Convert km/h to m/s
We are given:
- Speed limit = 120 km/h.
To convert km/h to m/s, we use the conversion factors:
- 1 kilometer = 1000 meters,
- 1 hour = 3600 seconds.
The conversion formula is:
Speed in m/s = Speed in km/h × (1000 / 3600)
Simplify the conversion factor:
1000 / 3600 = 5 / 18
Step 2: Calculate the speed in m/s
Substitute the values into the formula:
Speed in m/s = 120 × (5 / 18)
Speed in m/s = 600 / 18
Speed in m/s = 33.33 m/s
Final Answer:
The speed limit of 120 km/h in SI units is 33.33 m/s.
