P11: Pressure And Surfaces

Question 1

Why can a drawing pin push easily into a board, but it is impossible to make a hole with your thumb?

Answer 1

The pin is sharp so less surface area is being applied when it pushes against the board, unlike the thumb which has a bigger surface area.

Question 2

What is pressure?

Answer 2

The force per unit of area

Question 3

Calculated the pressure when 100N is applied to an area of 5m

Answer 3

100 / 5 = 20Pa

Question 4

What part of a container of water will have the highest pressure?

Answer 4

The bottom of the container

Question 5

Calculate the pressure of the water column of height 1m with P water (= 1000kg/m) and gravity (10N/kg)

Answer 5

1 x 1000 x 10 = 10,000 Pa

Question 6

Why does a water dam have a thicker base than top?

Answer 6

Because the water at the bottom of the dam is under more pressure so it needs more support

Question 7

How does atmospheric pressure change with elevation above sea level?

Answer 7

The higher you go above sea level, the lower the atmospheric pressure

Question 8

What is upthrust?

Answer 8

Upthrust is the upward force that a liquid or gas exerts on a body (or object) floating in it

Question 9

Why does an object sink?

Answer 9

An object sinks when its weight is greater than the upthrust provided by the fluid.

Question 10

Ice floats on water, what does this tell you about the density of the ice compared to the density of the water?

Answer 10

The density of the ice is lower than the density of the water