Force spread over area

Science · Forces & Motion · ages 15-16

Name ______________________ Date ____________

Why does a drawing pin pierce with little force?
- Its point has a tiny area
- Its point is cold
- Its point is heavy
How do you calculate pressure?
- Force times area
- Force plus area
- Force over area
What happens to liquid pressure as you dive deeper?
- It climbs
- It falls
- It stays flat
Water has a density of 1000 kilograms per cubic metre and the field strength is 10 N/kg. What is the extra pressure from the water 3 m below the surface, in pascals?
Answer: ______________
A force of 200 newtons acts on 4 square metres. What is the pressure in pascals?
Answer: ______________
A block floats in water but sinks in oil. What does that tell you?
- The block is denser than water but less dense than oil
- The block is less dense than water but denser than oil
- The oil pushes more than water
Why does air pressure fall on a mountain top?
- Cold air weighs nothing
- Less air piles above you, so less weight presses down
- Wind blows the pressure away
A student says upthrust comes from the top face pressing harder than the bottom. True or false?
Circle one: True False

Answer key

For grown-ups. Fold this page away before handing over the rest.

Its point has a tiny area · Shrinking the area rockets the pressure up.
Force over area · Pressure spreads a force over an area.
It climbs · The extra pressure from the liquid equals depth times density times field strength, so more depth means more pressure.
30000 · Multiply depth times density times field strength.
50 · Divide 200 by 4.
The block is less dense than water but denser than oil · Floating means less dense than the fluid.
Less air piles above you, so less weight presses down · With less atmosphere above, the pressing weight shrinks.
False · The bottom sits deeper, so it feels more pressure.