Physics 9702 · AS & A Level · Elastic and plastic behaviour

Elastic and plastic behaviour — practice question

(a)[1]

State Hooke’s law in words.

(b)

The way the force $F$ varies with compression $x$ for a spring is shown in Fig. 3.1. The spring is attached to the sealed end of a horizontal tube. A block is forced into the tube so that the spring becomes compressed, as shown in Fig. 3.2. The spring compression is $4.0\,\text{cm}$. The block has a mass of $0.025\,\text{kg}$.

(b(i))[2]

Calculate the spring constant for the spring.

(b(ii))[2]

Show that compressing the spring by $4.0\,\text{cm}$ gives a work done of $0.48\,\text{J}$.

(b(iii).1)[2]

The block is then released and speeds up along the tube as the spring returns to its original length. The block exits from the end of the tube at a speed of $6.0\,\text{m s}^{-1}$. Calculate the kinetic energy of the block as it leaves the end of the tube.

(b(iii).2)[3]

Assume that the spring has negligible kinetic energy when the block leaves the tube. Determine the average resistive force acting on the block as it travels along the tube.

(b(iv))[2]

Determine the efficiency of the transfer of elastic potential energy from the spring to the kinetic energy of the block.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Force (or load) is directly proportional to extension or compression so long as the proportionality limit is not exceeded

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