Ch 3.6 Under Pressure

Question 1

Why is the cutting edge of a knife made very thin

Answer 1

A sharp knife has a very thin edge to the blade. The sharp edge concentrates the force onto a very small area. The knife puts a high pressure on the wood. Blunt edges are no use for cutting. They spread out the cutting force, lowering the pressure.

Question 2

Concentrating the force on a small area gives a high pressure. Spreading the force over a large area gives a low pressure.

Question 3

(practise sums from book)

Question 4

LIQUID PRESSURE

Answer 4

Pressure in liquids is due to its weight. The pressure increases with depth. The deeper you go, the higher the pressure.

Question 5

At a depth of 30m, the water pressure is about 300, 000 N/m *2

Question 5

Why do deep sea divers wear protective suits?

Answer 5

The pressure increases with depth. The deeper you go, the higher the pressure. At a depth of 30m the water pressure is about 300,000
N/m *2.
Deep sea divers at the bottom of the ocean feel tremendous pressure. The pressure comes from the weight of the sea above them. The water presses in on the diver in every direction - from above and below and on both sides. This is why divers need suits to withstand this tremendous pressure.

Question 6

Pressure is greater at the bottom than at the top

Question 7

Pressure isn’t affected by the width and shape of a container with liquid. Proof - Pascal’s Vases

Question 8

Liquid pressure can be transmitted

Question 9

A Hydraulic Jack changes one small force into a bigger one (multiplies it)

Question 10

Working Principle -
The small downward force at a high pressure is changed to a large upward force