Physics 9702 · AS & A Level · Density and pressure

Density and pressure — practice question

A solid cylinder with weight $24\,\text{N}$ is formed from a substance of density $850\,\text{kg m}^{-3}$. Its length is $0.18\,\text{m}$, as illustrated in Fig. 1.1.
(a)[3]

Show that the cross-sectional area $A$ of the cylinder is $0.016\,\text{m}^2$.

(b(i))[1]

Show that the upthrust acting on the cylinder due to the liquid is $32\,\text{N}$.

(b(ii))[3]

Calculate the density of the liquid.

(c(i))[3]

Fig. 1.3 displays how the tension $F$ changes with the length of the spring in (b). The tap at the base of the container is opened so that a fixed amount of liquid leaves the container. The cylinder then moves downwards so that the tension in the spring changes from $8.0\,\text{N}$ to $4.0\,\text{N}$. Determine the change in the elastic potential energy of the spring.

(c(ii))[1]

Additional liquid is drained from the container until the upthrust on the cylinder is reduced to $24\,\text{N}$. For an upthrust of $24\,\text{N}$, determine the length of the spring.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Applying $m=\rho V$ or $m=\rho A L$

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