4.4. Speed http://www.ck12.org
time=distance
speedQ:If you walk 6 km at an average speed of 3 km/h, how much time does it take?
A:Use the formula for time as follows:
time=
distance
speed
=6 km
3 km/h
=2 hSummary
- How fast or slow something moves is its speed. The SI unit for speed is meters per second (m/s).
- Average speed is calculated with this formula:
speed=
distance
time- Speed may be constant, but often it varies from moment to moment. Speed at any given instant is called
instantaneous speed. It is much more difficult to calculate than average speed. - Distance or time can be calculated by solving the average speed formula for distance or time.
Vocabulary
- speed: How quickly or slowly something moves; calculated as distance divided by time.
Explore More
Do problems 1–3 on the average speed worksheet at the following URL.
http://www.mrjgrom.com/Physics%20resources/Speed_Problem_hw1.pdf
Review
- What is speed?
- If you walk 3 kilometers in 30 minutes, what is your average speed in kilometers per hour?
- Compare and contrast instantaneous and average speed.
- What distance will a truck travel in 3 hours at an average speed of 50 miles per hour?