Physics Topic Eleven

• when a force acts at a right angle to a surface, the force exerts pressure on the surface
• pressure is measured in pascals - one pascals is one newton per square metre
• a liquid will flow until the pressure along any horizontal line is constant
• the pressure in a liquid is calculated using: pressure = height above point x density x gravitational field strength
• the further down a liquid you go the greater the height above the point is so the greater the pressure
• the greater the density of a liquid, the greater the pressure of that liquid
• the atmosphere is a layer of air particles, atmospheric pressure is due to air molecules within Earth's atmosphere colliding with surfaces
• the higher altitude, the less weight of air is above that altitude so the lower the pressure and the less dense the air is as there's fewer molecules so the lower the pressure
• flat objects with a different pressure on either side will experience a force because of the pressure difference
• when a volume is in a fluid, it displaces a volume of liquid equal to its own volume
• pressure in a fluid increases with depth so the pressure exerted by a fluid is greater on the bottom of an object than the top. this means the upward force is greater than the downwards force, this is upthrust. the upthrust equals the weight of fluid displaced
• an object floats when its weight is equal to the upthrust and sinks when its weight is greater. an object less dense than the liquid will float and one denser will sink