chapter 6 - pressure

Question 1

pressure

Answer 1

force exerted by an object per unit area

Question 2

density

Answer 2

mass per unit volume

Question 3

conversion between kg/m3 to g/cm3

Answer 3

1000 kg/m3 = 1 g/cm3

Question 4

pascal’s principle

Answer 4

if a pressure is applied to a trapped liquid, the same pressure is transmitted to all parts of the liquid

Question 5

explain the crushing can experiment

Answer 5

• when heating the water until its boiling point, it produces steam that rushes out of the can, removing some air from the inside, creating a partial vacuum
• when removing the can from the heat and screwing the cap on, the air inside is trapped and no air can enter or escape from the can
• when placing the can under running water, the steam inside condenses, removing more gas
• the can crumples as the atmospheric pressure is the surrounding is larger than the pressure inside the can as a partial vacuum has been created inside
• humans are not crushed like the can as the pressure in our body (eg. blood pressure) is balanced with the atmospheric pressure

Question 6

explain how to use a manometer to find the pressure of a gas

Answer 6

• if source column taller than open column, pressure of gas = atmospheric pressure - mmhg
• if source column shorter than open column, pressure of gas = atmospheric pressure + mmhg

Question 7

how does the molecules inside the cylinder create a pressure

Answer 7

the air molecules in the container are moving at very high speeds in random directions. as they collide with the inner walls of the containers and with one another, they exert a force to be exerted by each of the collisions, due to the large number of air molecules colliding at a high frequency, a large force is exerted on the container, and since pressure is force per unit area, this creates a large pressure

Question 8

why hydraulic press does not work properly if oil contains air bubbles

Answer 8

pressure is not able to transmit uniformly throughout the oil as air is compressible and results in a loss of pressure and reduction in the force.

Question 9

how does heating the gas cause a greater pressure

Answer 9

temperature increase, kinetic energy of gas molecules increase, collide with walls more vigorously and frequently, average force increase, pressure increase