| Date | May 2014 | Marks available | 1 | Reference code | 14M.1.SL.TZ2.9 |
| Level | Standard level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | Question number | 9 | Adapted from | N/A |
Question
Two particles, X and Y, are attached to the surface of a horizontally mounted turntable.
The turntable rotates uniformly about a vertical axis. The magnitude of the linear velocity of X is v and the magnitude of its acceleration is a. Which of the following correctly compares the magnitude of the velocity of Y and the magnitude of the acceleration of Y with v and a respectively?
Markscheme
D
Examiners report
There was much guessing here with even A and C being popular options. This would suggest that many candidates had not understood the situation – surely a fly near the hub of spinning bicycle wheel is going slower than one perched on the rim. So A and C should have
been instantly discounted through the application of commonsense. Since the velocity and also the radius is changing from situation X to Y, it is easier to use the formula a = ω2r (where ω is constant) to ascertain that the acceleration at Y is greater. Alternatively, you can imagine that Y is on the outer edge of a fairground big wheel in order to realize that the forces upon you (and hence acceleration) will be greater.
