Stretching Materials (Edexcel International A Level Physics)

A student carried out an experiment to determine the Young modulus of a sample of stainless steel in the form of a wire. The student added weights to the wire and measured the corresponding extensions.

The wire had an unstretched length of 2.6 m. The diameter of the wire was 5.6 × 10^–4 m.

The student plotted a graph of weight against extension. The graph showed that the limit of proportionality was not exceeded.

The student's graph is shown below.

(3)




Young modulus = ........................................

*The photograph shows a toy car that contains a spring. Pulling the car backwards along the floor compresses the spring. Energy is stored in the compressed spring.

The car is released and the spring returns to its original state. There is a forward force on the car from the floor and the car moves forwards.

Explain why the floor exerts a forward force on the car and how this force affects the motion of the car as the spring returns to its original state.

The photograph shows a toy pinball machine. The launcher is pulled back, compressing a spring. The spring obeys Hooke’s law. When the launcher is released, the spring returns to its original length and a small ball is launched horizontally into the machine.

When the launcher is pulled back, the spring is compressed by 5.0 cm. When the spring is released, the ball is launched at a speed of 8.0 cm s⁻¹.

(2)

Determine the force on the ball when the spring is released.

Force = ................................

Determine the stiffness of the spring.

Stiffness = ..............................

The spring returns to its original length L. 

Sketch a graph, on the axes below, to show how the velocity of the ball varies with the length of the spring.