Forces And Pressure Flashcards
What is pressure?
Pressure is the force per unit area. The unit of pressure is the pascal (Pa) which is equal to one newton per square metre (N/m*2).
What is the equation for pressure?
Pressure = force (N) / area (m*2).
What happens to the pressure of a liquid with depth?
The pressure of a liquid increase with depth.
What does the pressure in a liquid depend on?
The pressure in a liquid depends on the density of the liquid.
How do you calculate the pressure t the bottom of a liquid column?
Pressure = height x density x gravitational field strength.
What is atmospheric pressure?
Atmospheric pressure is due to air molecules colliding with surfaces. Each impact exerts a tiny force on a surface, but the number of molecules that collide with the surface per second is very large.
What happens to the density of the atmosphere is terms of height?
The density of the atmosphere decreases with increasing height above the ground. Eg increasing altitude. This is because the weight of air pressing down on a horizontal surface at any altitude decreases with altitude. So there are fewer molecules per cubic metre and therefore fewer impacts per second at higher altitude. So, atmospheric pressure decreases with increasing altitude. In effect, the weight of air above any given altitude exerts pressure in the air below. At increased altitude, there is less weight of the air above, so the atmospheric pressure decreases with increasing altitude.
Explain upthrust.
The water level in a water container rises when an object is lowered into the water. this is because the object displaces some of the water.
The more the object is lowered into the water, the bigger the volume of water displaced. Therefore, the bigger the upthrust.
When the object is fully immersed, the volume of water displaced is equal to the volume of that object.
When will an object float?
An object will float when its weight is equal to the upthrust.
Objects that float have a density less than the density of the water.
An object that is less dense than the liquid floats because its weight is less than the weight of the liquid it displaces. So the weight of the object is less than the upthrust on the object when it is fully immersed.
When will an object sink?
An object sinks when its weight is greater than the upthrust.
Objects that sink have a density higher than the water.
