Pressure

If we know the size of the force (F) and the area over which the force is applied (A), then we can calculate pressure using

P = \displaystyle {F \over A}

Here is the outline of a pupil’s shoe, it’s drawn on graph paper so that the area can be calculated quickly by counting the large squares.  Each large square is 1 square centimetre – we counted the approximate area by considering only whole squares inside the black outline of the shoe.

shoe outline

Assuming a mass of 50kg, the pressure when wearing these flat-soled shoes is

P = \displaystyle {{(50 \times 9.8)N} \over {0.0306m^2}} = 16000Nm^{-2}

The red shaded area of our photo shows the reduction in area when heels are worn.  With heeled shoes, the area is reduced to approximately 1 square cm per shoe.  The change in the pressure is staggering:

P = \displaystyle {{(50 \times 9.8)N} \over {(0.0002)m^2}} = 2450000Nm^{-2}

The Science Babe has made a video on this topic.

national 5 exam questions – electricity and energy

Here are the exam-style questions to cover the electricity and energy unit.  I have included a copy of the relationships (equation) sheet and some data tables that you may need to attempt all the questions.  Apologies for the larger file size, it’s due to all the circuit diagrams.

Use the link below to download your own copy.