A grade 9 learner uses her thumb to push a drawing pi into a soft board. Which of the following statements is correct?

Here are the answers to the questions:

1. A grade 9 learner uses her thumb to push a drawing pin into a soft board.
The pressure exerted by a force is inversely proportional to the area over which the force is applied ($P = \frac{F}{A}$). The tip of the drawing pin has a much smaller surface area than the head of the pin. Therefore, for the same force applied by the thumb, the pressure at the tip (on the soft board) will be much greater than the pressure on the head (from the thumb).

The correct statement is:
D The pressure on the soft board is greater because the surface area is smaller.

2. Which instrument is used to measure pressure?
A barometer measures atmospheric pressure, and a manometer measures gas pressure or pressure differences. Both are instruments for measuring pressure. Among the given options, a manometer is a general instrument for measuring pressure.

The correct instrument is:
B manometer

Structured Questions
1. State the influence of the following factors on the pressure in a liquid.
The pressure in a liquid is given by the formula $P = \rho g h$, where $P$ is pressure, $\rho$ is the density of the liquid, $g$ is the acceleration due to gravity, and $h$ is the depth.

• a) Depth Pressure in a liquid increases with increasing depth. This is because pressure is directly proportional to depth ($P \propto h$).

• b) Density of the liquid Pressure in a liquid increases with increasing density of the liquid. This is because pressure is directly proportional to the density of the liquid ($P \propto \rho$).