Presentation on theme: "Pressure. Pressure in solids Core Relate (without calculation) pressure to force and area, using appropriate examples Extension Recall and use the equation."— Presentation transcript:
Pressure in solids Core Relate (without calculation) pressure to force and area, using appropriate examples Extension Recall and use the equation p = F/A
Pressure Forces are pushes, pulls and twist. Pressure is a measure of how spread out a force is. As you in increase the size of the force you increase the size of the pressure. As you increase the size of the area over which a force acts, you decrease the pressure. Less pressure More pressure Less pressure More pressure
Pressure questions 1.Why do tractors have such large tyres? The tyres have a large area so that the weight of the tractor is spread over a large area. This reduces the pressure the tractor puts on the ground, so that it doesn’t sink into the mud.
Why would a lady in stiletto heels standing on your foot hurt you more than a elephant standing on your foot? The elephant has a greater weight than the lady and it would have a greater pressure if the area the weight acted upon was the same. However, the lady’s weight is concentrated into a smaller area than that of the elephant’s. This means that the stiletto heel exerts a greater pressure than the foot of the elephant, and might hurt more.
P=F/A Suplement We can express the pressure formula using the equation: Pressure = Force ÷ Area P =F/A Pressure measured in pascals (Pa) Force measured in newtons (N) Area measured in metres squared (m 2 )
Formula triangles F P AA x Formula triangles help you to rearrange formula. The triangle for the pressure formula is shown below: Whatever quantity you are trying to find, cover it up and it will leave you with the calculation required. So if you were trying to find pressure, P….. …you would cover P up… …and you are left with the sum… P = F A
Pressure calculations: 1.What pressure will a force of 20N acting over an area of 4 ms -2 put upon the ground? 2.A force of 50N acts on an area and creates a pressure of 1.0Pa. Over what area is the force acting? 3.A pressure of 6 000 Pa is created by a force acting on an area of at 5 m 2. What is the size of the force? Pressure = 5 Pa Area = 50 m 2 Force = 30 000 N