2Pressure – 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
3Pressure 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
4Pressure 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
5Some 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?
113 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)
12Moment (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
13Balancing 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