Figure 3 shows a garden gate with a pulley system designed to close the gate - AQA - A-Level Physics - Question 3 - 2022 - Paper 1

To determine which material is used for weight A, we need to calculate the volume of A first using the volume formula for a cylinder:

$V = ext{area} imes ext{length}$

The cross-sectional area (A) is calculated as:

A = rac{ ext{diameter}^2 imes ext{π}}{4} = rac{(4.8 imes 10^{-2})^2 imes ext{π}}{4} \ ext{Area} \ = 1.8 imes 10^{-3} m^2

Now we calculate the volume:

$V = A imes ext{length} = 1.8 imes 10^{-3} m^2 imes 0.23 m = 4.14 imes 10^{-4} m^3$

The mass of weight A is given by:

$m = \frac{ ext{weight}}{g} = \frac{35 ext{ N}}{9.81 ext{ m/s}^2} = 3.57 ext{ kg}$

Next, we calculate the density using the formula:

$\text{Density} = \frac{m}{V} = \frac{3.57 ext{ kg}}{4.14 imes 10^{-4} m^3} = 8.63 imes 10^3 ext{ kg/m}^3$

Comparing with the given densities, we find that brass is the material used for A.