What will happen – Why? When the barrier is removed, what will happen and can you explain why?

What will happen – Why?

Which is the odd one out? Why?

Pressure Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain up thrust

Pressure F P = A Pressure is defined as the force per unit area. m2 Pa or N/m2 1 Pa (Pascal) = 1N/m2 Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Pressure A box of chocolates weighs 180 N. Its base has an area of 0.09 m2. What pressure does it exert on the ground? P = F A P = ? F = 180 N A = 0.009 m2 P = 180 0.009 P = 2000 Pa Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Walking on Ice-cream Samantha who has a mass of 51kg wants to walk over a pool full of ice-cream. If she exerts a pressure greater than 280 Pa she’ll fall into the ice-cream. How big will she have to make her shoes?

Pressure Pressure in liquids: Pressure (N/m2) = 10 N/kg x depth (m) x density (kg/m3) The pull of gravity The greater the depth, the higher the pressure The denser the liquid, the heavier it is

Pressure The deeper in the bottle the more water there is above that point. Therefore there is more mass above (mass is proportional to weight). So the deeper you go the more weight is pushing down on you and the higher the pressure is. This pressure pushes the water out at a greater speed. The deeper you go the higher the pressure the faster the waters is pushed out.

Pressure A challenge: Can you show that the equation for pressure in a solid is the same as pressure in a fluid?

Pressure Pressure = ρgh A diver is 12m beneath sea level, assuming that water has a density of 1000kg/m3 How much greater would the pressure be if he had dived in syrup, with a density of 1330kg/m3 A submarine is 1.3km beneath sea level, assuming that water has a density of 1000kg/m3 EXT1: How deep would a diver be beneath the water if the pressure were 240,000 Pa. EXT2: Sea waters actual density is 1027kg/m3 because of the additional salt. Recalculate Q1 and 3 with this new value. Pressure = ρgh

Pressure = 0.1 m3 Average area of a human (looking down on them) The force exerted on a human by the air in a column directly above is 101330 N = 0.1 m3 What is the pressure exerted on the human? What assumptions have been made in this calculation.

Pressure

The Atmosphere The atmosphere is a thin layer of gas surrounding the Earth. It gets less dense the higher you go. The higher you go, the lower the pressure.

The Atmosphere A gas exerts a pressure on a surface by the collision of gas particles with that surface. The particles exert a force normal (perpendicular) to the surface. The more particles (the denser the gas) able to collide, the higher the pressure. The faster the particles are moving (the hotter the gas) the greater the pressure.

Pressure Atmospheric pressure is equal to 100,000 Pa or 100 Kpa. As this pressure is present both above and below objects in the lower atmosphere the forces are in equilibrium therefore no resultant force is exerted. So… how could I do this?

Pressure Imploding Bottles When you seal a bottle the pressure inside and outside are in _________. If pressurised at high altitude the pressure inside the bottle will be _______ than if it had been pressurised at sea level. When the bottle is taken ______ the mountain / hill it will gradually compress as the pressure on the outside is ________ than the pressure inside.

Upthrust

To begin with ... Explaining why Pressure To begin with ... Explaining why Can you pull the Madeburg hemispheres apart? Why is this happening? Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Pressure A vacuum is a space where there are no particles at all The pressure outside the hemispheres is greater than the inside This pushes them together Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Pressure Atmospheric pressure us about 100 000Pa (although it changes day to day) That like having one kilogram resting on every square centimetre of your skin! Pressure How come you don't notice this pressure? The fluids inside your body are of a similar pressure so it evens out Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Manometer We can measure the air pressure using a manometer Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Manometer When the pressure acting on the left equals the pressure on the right the height either side of the manometer is the same Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Manometer The pressure on the left (the air pressure) is the same as before BUT the pressure on the right is now bigger (different gas) So for it to be even… The air pressure AND the pressure caused by the difference in height from the liquid can then balance. And luckily… we have an equation for that BRILLIANT + = Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Manometer REALLY IMPORTANT The manometer measures the difference in the pressure between two gasses Therefore if you want the actual pressure of the gas you need to add that on to what you have found using the equation Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Barometer The barometer works in a slightly different way. This has a vacuum at the top, so rather than comparing two different gases it gives you the pressure of the gas acting on the surface- this is difficult to use with anything other than air pressure Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

Mercury Barometer When we use a Mercury barometer (Very heavy liquid) we can use a different unit of measurement. mmHg Millimetres of mercury … Is just that, can just measure the difference in height in mm Atmospheric pressure is 760mmHg Be able to use the equations for pressure and the appropriate units. Describe and explain pressure in solids, liquids and gases. Apply knowledge of pressure to explain hydraulic systems

MOTION Know the difference between vectors and scalars Data Logger Know the difference between vectors and scalars Use distance time graphs to describe the motion of an object Be able to calculate the velocity/acceleration from the gradient