Pressure

Question 1

Devni and James are discussing water pressure. Devni thinks that the pressure exerted by a liquid depends on the density of the liquid. James thinks that density is not as important, as the pressure is the same in all liquids. Who is correct, Devni or James?

Answer 1

devni; The more dense the liquid the more mass it will have. The higher the mass, the larger the force of its weight pushing down will be.

Question 2

Air molecules colliding with a surface create __________ pressure. What word completes the sentence?

Answer 2

atmospheric; The atmosphere is made of air, so the pressure due to air is called atmospheric pressure.

Question 3

Julian is 168 cm tall. Frank is 174 cm tall. True or false? There are more air molecules above Julian’s head than there are above Frank’s head, when they stand next to each other.

Answer 3

true; Julian is shorter than Frank, so there is a larger volume of air above Julian.

Question 4

What happens to the atmospheric pressure as the distance above the ground increases?

Answer 4

it decreases; As the distance above the ground increases, the weight of air above decreases, so pressure decreases.

Question 5

what is the formula to find pressure?

Answer 5

pressure = force /area

Question 6

The atmosphere gets less __________ with increasing altitude. What is the missing word in this sentence?

Answer 6

dense; The higher the altitude, the fewer particles there will be, because there is less weight of particles above pushing them together. Density is a measure of the number of particles per cubic meter.

Question 7

An object is submerged in liquid. The object’s weight is greater than the upthrust on it. Will the object float?

Answer 7

no; If the weight is greater than the upthrust, then the resultant force will be downwards, and the object will accelerate downwards and sink.

Question 8

An object is placed in a liquid. The object’s weight is equal to the upthrust on it. Will the object float or sink?

Answer 8

float; If the weight is equal to the upthrust, then the resultant force will be zero, so the object will float.

Question 9

Kevin wants to add some pizzazz to his pet fish’s tank, so he buys a miniature castle and places it in the water. The castle is denser than the water, so the volume of water that it displaces has a weight __________ __________ the castle’s weight. Which phrase completes the sentence?

Answer 9

less than; The castle is more dense than the water, so the water it displaces will have a lower mass and consequently a lower weight than the castle.