Pressure and Moments

Why is it easier to cut something with a sharp knife than with a blunt one?

• The area of the knife edge is large so pressure is greater.

• The area of the knife edge is small so pressure is greater.

• The area of the knife edge is large so pressure is smaller.

• The area of the knife edge is small so pressure is smaller.

If all these birds are the same weight, which bird has the lowest pressure under its feet?

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• 
• 
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A basketball player weighs 500 N. The area of one of his trainers is 250 cm².

When he puts all his weight on one foot, how much pressure does he put on the ground?

• 0.5 N/cm²

• 2 N/cm²

• 250 N/cm²

• 125 000 N/cm²

The pressure in liquids and gases is caused by

• the particles pressing down.

• the particles pushing up.

• the particles moving sideways.

• the particles moving in all directions and colliding with things.

Why does a dam at the end of a lake need to be wider at the bottom?

• Water pressure is greater near the surface of the water.

• There is more water pressure at the bottom of the lake.

• To use up more concrete.

• Water pressure decreases with depth.

When a gas is compressed:

• the particles bump into the walls of the container less often.

• the pressure drops.

• the particles become more spread out.

• the pressure increases.

A hydraulic system:

• uses air to smooth out bumps.

• uses air to send a force from one place to another.

• uses a liquid to send a force from one place to another.

• uses a solid to send a force from one place to another.

In science, a lever is:

• a complex machine which keeps the size of force you put in the same.

• a simple machine which changes the size of force you put in.

• a simple machine which changes the area of force you put in.

• someone about to finish school.

Which are the correct labels for the lever shown below?

• X = effort, Y = pivot, Z = load

• X = pivot, Y = effort, Z = load

• X = load, Y = pivot, Z = effort

• X = load, Y = effort, Z = pivot

Which lever will make it easiest to move the rock?

• A

• B

• C

• D