Topic 5 Forces, density and pressure - chapter 7

Question 1

what is density?

Answer 1

density is a property of matter that tells us how concentrated the matter is in a particular material.

Question 2

what is the formula of density?

Answer 2

density (kg m^-3) = mass(kg) / volume(m^3)

Question 3

what is pressure?

Answer 3

pressure is defines as the normal force acting per unit cross-sectional area.

Question 4

what is the formula of pressure?

Answer 4

pressure(pa) = normal force(N) / cross-sectional
area(m^2)
1 pa = N m^-2

Question 5

what is the density of water?

Answer 5

1000 kg m^-3

Question 6

what are the factors that affect pressure in a fluid?

Answer 6

• depth (h) below the surface
• density of a fluid
• acceleration due gravity (g)

Question 7

what is the relationship between factors that affect pressure and pressure?

Answer 7

they are all directly proportional to pressure
therefore,
pressure = depth * density * acceleration due gravity

Question 8

what is the formula of pressure?

Answer 8

pressure = force / cross-sectional area

force = weight = mg
density = mass / volume
therefore,
mass = density * volume

hence,
force = m * g = (density * volume) * g

therefore,
pressure = force / cross-sectional area
= (DENSITY * VOLUME * g) / CROSS-
SECTIONAL AREA

volume = cross-sectional area * depth

therefore,
pressure = (density * cross-sectional area * depth * g)
/ cross-sectional area

cancelling out cross-sectional area,

pressure = DENSITY * DEPTH * g