HardPhysicsHigh School (11–12)Mechanics › Relative MotionMechanics › Motion in a Straight LineNumerical
Car A leaves a town at a steady 36 km/h.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Car A leaves a town at a steady . Car B leaves the same spot minutes later at , the same way. How long after B starts does it catch A, and how far from the town?
Need a reminder? The key ideaShow
Along a line, , with signs. The same way: subtract the speeds. Opposite ways: add them. Time to meet gap closing speed. To change km/h to m/s, multiply by .
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. The head start. .
Step 2. The catch. B gains , so .
Step 3. Where. .
Answer: after B starts, from the town.
Check. A has driven by then: .
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