P11 Pressure

Question 1

Equation for pressure in a liquid

Answer 1

Pressure = height of column of liquid x gravitational field strength x density of liquid

Question 2

What is atmospheric pressure?

Answer 2

Aire molecules colliding with a surface create atmospheric pressure
Number of air molecules decreases as height above sea level increases
So atmospheric pressure decreases with and increase of height

Question 3

Atmospheric Pressure equation

Answer 3

Pressure = height x density x gravity

Question 4

What is upthrust?

Answer 4

When an object is submerged the pressure the fluid exerts a force onto it from every direction
Pressure increases with depth so force acting on bottom of object is larger than force exerted on top of object
This resultant force is known as upthrust

Question 5

When does an object sink?

Answer 5

When the object is more dense than the water the weight is always larger than the upthrust so it sinks.

Question 6

When does an object float?

Answer 6

When an object is less dense than water so it displaces a volume of liquid equal to it’s weight before it completely submerges, then it floats. At this point objects weight is equal to upthrust so it floats