Physics (AS & A Level) · May / June 2019 · Paper 11 · Question 21

A 0.80 m length of steel wire and a 1.4 m length of brass wire are joined together. The combined wires are suspended from a fixed support and a force of 40 N is applied, as shown. The Young modulus of steel is 2.0 × 10^11 Pa. The Young modulus of brass is 1.0 × 10^11 Pa. Each wire has a cross-sectional area of 2.4 × 10^-6 m^2. The wires obey Hooke's law. What is the total extension? Ignore the weights of the wires.

1. A1.7 × 10^-4 m
2. B3.0 × 10^-4 m
3. C3.9 × 10^-4 m
4. D9.0 × 10^-4 m

As printed in the paper