P11 Force and Pressure

Question 1

What is the formula for pressure?

Answer 1

p=F/A

pressure (p) is measured in pascals (Pa)
force (F) is measured in newtons (N)
area (A) is measured in metres squared (m2)

Question 2

What is a Pascal equal to

Answer 2

1Newton/meter square
1 N/m^2

Question 3

What is pressure?

Answer 3

Force per unit area

Question 4

The pressure across a horizontal line in a liquid is ___?

Answer 4

constant

Question 5

What is the formula for pressure caused by a column of liquid?

Answer 5

pressure = height of column × density of the liquid × gravitational field strength
p=hρg

This is when:

pressure (p) is measured in pascals (Pa)
height of column (h) is measured in metres (m)
density (ρ) is measured in kilograms per metre cubed (kg/m3)
gravitational field strength (g) is measured in newtons per kilogram (N/kg)

This formula tells us that the greater the density the greater the pressure.

Question 6

How is air pressure created?

Answer 6

Tiny air particles collide with a surface and apply a force on them.

Question 7

Why is there less pressure on a higher altitude?

Answer 7

There is less air particles .

Question 8

What is the pressure difference formula?

Answer 8

F=PxA

F= Force on a flat surface due to a pressure difference
P=Pressure Difference
A=Flat surface area

Question 9

What is upthrust?

Answer 9

It is a force that pushes things upwards. This happens when a gas or liquid has an object floating in it. It happens due to the pressure above and below a liquid as pressure increases with depth of liquid.

Question 10

What would happen if the upthrust is less/greater than the weight of the object immersed in the liquid?

Answer 10

If the upthrust force is less than the weight of the object, the object will sink.

If the upthrust force is greater than the weight of the object, the object will float.

Question 11

What would happen if the objects density is greater than the fluids density.

Answer 11

Since the density is greater in the object, the fluid cannot displace enough fluid to create a balanced upthrust so the object sinks.

Question 12

Why does a plastic ball float?

Answer 12

pressure of water on lower half of ball > on top half so ball experiences
upthrust,
volume of liquid displaced by ball = volume of ball,
as water is much denser than air, weight of liquid displaced much >
weight of ball
so upthrust on ball much > weight

Question 13

Why does an empty water bottle crush when the plane has landed

Answer 13

Whilst flying the air in the bottle is at lower pressure so there are fewer air molecules.On landing the air pressure is greater outside the bottle than inside.
Therefore the bottle crushes inwards.