Physics (AS & A Level) · Feb / March 2021 · Paper 12 · Question 14

A balance is used to measure the mass m of a number of cylindrical metal rods of length l. All the metal rods have the same radius r. The graph shows the variation with l of m. [graph of m against l, straight line through origin] The gradient of the graph is G. Which expression gives the density of the metal?

1. A\frac{G}{2\pi r}
2. BG2\pi r
3. C\frac{G}{\pi r^2}
4. DG\pi r^2

As printed in the paper