What you’ll learn
Use dimensional analysis.
Key idea
Length conversion changes the numerator; converting the time denominator requires seconds per hour, not minutes per hour.
Cancel units in numerator and denominator independently; intermediate meters/hour is not meters/second.
Worked example
Enter the exact value or ordered values in the format requested below.
Convert 108 km/hour to m/second. Use 1 km=1000 m and 1 hour=3600 seconds. Enter numerical m/s, omitting unit.
- 108 km/hour×1000 m/km=108000 m/hour.
- Multiply by 1 hour/3600 seconds: 30 m/s; reversing 30×3600/1000=108 km/hour.
Answer: 30
Quick Check
Evaluate a worked attempt at use dimensional analysis, identify the first invalid step, and provide the correction.
Use 1 km=1000 m and 1 hour=3600 seconds. Converting 18 km/hour: Step 1 gives 18000 m/hour. Step 2 divides by 60 and labels 300 m/second. Locate the first invalid step and repair the speed.