Pressure, Force & Area

Grade 5

What pressure means

Pressure is how much force is pushing on a given area. A sharp pin hurts because all the force is concentrated onto a tiny area — high pressure. Snow shoes spread your weight over a large area — low pressure.

Pressure = Force ÷ Area

The standard unit is N/m² (newtons per square metre), also called a pascal (Pa).

The triangle

Same structure as speed and density: put F at the top, P × A at the bottom.

Force = Pressure × Area. Area = Force ÷ Pressure. Pressure = Force ÷ Area.

Worked example — finding pressure

EXAMPLE

A force of 600 N acts on an area of 0.3 m². Calculate the pressure.

Pressure = Force ÷ Area = 600 ÷ 0.3 =2000 N/m².

Worked example — finding area

EXAMPLE

A block exerts a pressure of 400 N/m² with a force of 200 N. What area is the block resting on?

Area = Force ÷ Pressure = 200 ÷ 400 =0.5 m².

All three triangles follow the same pattern

Speed, density, and pressure all use the same divide-multiply structure. If you're solid on one of them, the other two follow automatically — just swap in the right letters and units. The only things that change are the quantities and their units.

Try this one

A train travels at 90 km/h for 40 minutes, then at 60 km/h for 30 minutes.

(a) Find the total distance the train travels. [2]

(b) A car travels the same total distance in 1 hour 15 minutes. Find the average speed of the car in km/h. [2]

Nova's hint:

This uses speed, distance, time with unit conversion.

Ask yourself: 'Have I converted the times into hours before using Distance = Speed × Time?' For example, 20 minutes = 20/60 = 1/3 of an hour.

Try to Solve it with Nova?