1 (a) Figure 1 shows air inside a cylinder with a movable piston - Edexcel - GCSE Physics - Question 1 - 2018 - Paper 1

The angle that this outward force makes with the wall of the tube is 90 degrees. The force exerted by the air is perpendicular to the surface of the wall.

To find the volume of air inside the tube, we can use the formula derived from the ideal gas law:

$P_1 \times V_1 = P_2 \times V_2$

Substituting the values:

$400000 \times V_1 = 100000 \times 4.8$

Rearranging gives:

$V_1 = \frac{100000 \times 4.8}{400000} = 1.2 \text{ litres}$

The air in the bicycle pump gets warm because work is done in compressing the air. This increases the kinetic energy of the air particles, which raises the thermal energy of the system. The relationship between work done and thermal energy can be expressed as:

$W = F \times d = p \times \Delta V$

where $W$ is work, $F$ is force, $d$ is distance, $p$ is pressure, and $\Delta V$ is the change in volume.