Rohit runs one full lap of a circular 300 m track in 75 s.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Rohit runs one full lap of a circular track in .
- What is his average speed?
- His average velocity?
- Why are they different?
- Halfway round, after , how far is he from the start in a straight line?
Need a reminder? The key ideaShow
Speed distance time; velocity displacement time. Average speed total distance total time. .
Distance is the length of the whole path; it has no direction and never decreases. Displacement is the straight line from start to end, with a direction. On a straight road use signs; for a right-angle turn, displacement .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) .
Step 2. (b) He ends where he started: displacement , so average velocity .
Step 3. (c) Speed uses the whole path; velocity uses only start and end.
Step 4. (d) Circumference , so .
Answer: ; ; .
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