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Published byJamie Fairleigh Modified about 1 year ago

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Pressure and Moments

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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

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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

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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

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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?

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Some examples of pressure

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Gas Pressure

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Hydraulic systems

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Pressure is constant throughout this liquid

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Levers Load Effort Pivot

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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)

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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

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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

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Balanced or unbalanced?

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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

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