MediumPhysicsHigh School (11–12)Mechanics › Vectors and Motion in a PlaneConceptualBoard ExamAPA-LevelIB
A car goes round a bend at a steady 15 m/s…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A car goes round a bend at a steady . Its speedometer needle never moves.
- Is the car accelerating?
- If it is, which way does the acceleration point?
- What would a passenger holding a cup of tea notice?
Need a reminder? The key ideaShow
Velocity is a vector. It changes when its size changes, when its direction changes, or both. Any change in velocity is an acceleration.
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. Is it accelerating? Yes. The speed stays the same, but the direction of the velocity keeps turning. A change in direction is a change in velocity, so the car is accelerating.
Step 2. Which way? The change in velocity, between two nearby points of the bend, points towards the inside of the bend. So the acceleration points towards the centre of the curve, at right angles to the velocity.
Step 3. The tea. The tea tends to keep going in a straight line while the car turns away under it. So the tea moves towards the outside of the bend, and may spill.
Answer: (a) Yes. (b) Towards the centre of the bend. (c) The tea moves towards the outside of the bend.
Watch out. "Steady speed" does not mean "no acceleration". It means only that the acceleration has no part along the motion.
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