2 Pressure – some basic ideas Describe and draw experiments for each of the following ideas:Pressure increases with depthPressure is the same in all directions at a certain depth
3 Pressure Explain how the following work: A sharp knife is easier to use then a blunt knifeA drawing pinA woman with stilettos on might damage a floor more than an elephant would
4 Pressure F A P Pressure depends on two things: How much force is applied, andHow big (or small) the area on which this force is applied is.Pressure can be calculated using the equation:FAPPressure (in N/m2) = Force (in N)Area (in m2)OR in cm2 and N/cm2
5 Some pressure questions Calculate the pressure exerted by a 1000N elephant when standing on the floor if his feet have a total area of 1m2.A brick is rested on a surface. The brick has an area of 20cm2. Its weight is 10N. Calculate the pressure.A woman exerts a pressure of 100N/cm2 when standing on the floor. If her weight is 500N what is the area of the floor she is standing on?(Hard!) The pressure due to the atmosphere is 100,000N/m2. If 10 Newtons are equivalent to 1kg how much mass is pressing down on every square centimetre of our body?
11 3 types of lever Load is on other side of pivot (e.g. seesaw) Load is “outside” the effort, (e.g. biceps)Load is “inside” the effort (e.g. wheelbarrow)
12 Moment (in Nm) = force (in N) x distance from pivot (in m) MomentsA moment is a “turning force”, e.g. trying to open or close a door or using a spanner. The size of the moment is given by:Moment (in Nm) = force (in N) x distance from pivot (in m)Calculate the following turning moments:5 metres100 Newtons2 metres200 Newtons
13 Balancing moments 2 metres 2 metres Total ANTI-CLOCKWISE turning moment = 200x2 = 400NmTotal CLOCKWISE turning moment = 100x2 = 200Nm200 Newtons100 NewtonsThe anti-clockwise moment is bigger so the seesaw will turn anti-clockwise