Presentation on theme: "Pressure and Moments. Pressure – some basic ideas Describe and draw experiments for each of the following ideas: 1)Pressure increases with depth 2)Pressure."— Presentation transcript:
Pressure and Moments
Pressure – some basic ideas Describe and draw experiments for each of the following ideas: 1)Pressure increases with depth 2)Pressure is the same in all directions at a certain depth
Pressure Explain how the following work: 1)A sharp knife is easier to use then a blunt knife 2)A drawing pin 3)A woman with stilettos on might damage a floor more than an elephant would
Pressure Pressure depends on two things: 1)How much force is applied, and 2)How big (or small) the area on which this force is applied is. Pressure can be calculated using the equation: Pressure (in N/m 2 ) = Force (in N) Area (in m 2 ) F AP OR in cm 2 and N/cm 2
Some pressure questions 1)Calculate the pressure exerted by a 1000N elephant when standing on the floor if his feet have a total area of 1m 2. 2)A brick is rested on a surface. The brick has an area of 20cm 2. Its weight is 10N. Calculate the pressure. 3)A woman exerts a pressure of 100N/cm 2 when standing on the floor. If her weight is 500N what is the area of the floor she is standing on? 4)(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?
Some examples of pressure
Pressure is constant throughout this liquid
Levers Load Effort Pivot
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)
Moments A 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: 100 Newtons 5 metres 200 Newtons 2 metres
Balancing moments 100 Newtons200 Newtons 2 metres Total ANTI-CLOCKWISE turning moment = 200x2 = 400Nm Total CLOCKWISE turning moment = 100x2 = 200Nm The anti-clockwise moment is bigger so the seesaw will turn anti-clockwise
Balanced or unbalanced?
Stability 1. Centre of mass is within the wheelbase – no problem! 2. Centre of mass is directly above the edge of the wheelbase –car is on the point of toppling 3. Car falls over