Pressure

Question 1

What is pressure?

Answer 1

• The force per unit of area
• The concentration of a force

Question 2

Equation for pressure

Answer 2

• Pressure (Pa) = Force (N) / Area (m2)

Question 3

What component of the force do we measure with pressure?

Answer 3

• The perpendicular force
• The component of the force that is at a right-angle to the surface it collides with

Question 4

Pressure in solids vs fluids

Answer 4

• Pressure in solids: the collision between two solids causes pressure
• Pressure in fluids: the collision between the fluid particles and a solid container causes pressure

Question 5

Why does atmospheric pressure decrease as height above sea level increases?

Answer 5

• Atmospheric pressure is caused due to collisions between air particles and the surface
• As height above sea level increases, the number of air particles decreases (as the air becomes less dense)
• This means that less collision take place overall, leading to a lower atmospheric pressure

Question 6

What happens to the pressure on an object as it gets deeper in a liquid?

Answer 6

• As the height of the column of liquid increases, the pressure increases aswell
• The greater the amount of liquid above the object, the greater the pressure

Question 7

Why is pressure of an object in liquid affected by the height of the column?

Answer 7

• Pressure in a liquid is caused by the weight of the liquid pushing against the object that is submerged in water
• If the object is deeper in the liquid, the aount of liquid above increases and therfore, the weight of the liquid increases and therfore, the pressure increases

Question 8

How does density effect pressure in a liquid?

Answer 8

• A more dense liquid has a greater weight and therefore, will exert a greater pressure

Question 9

Equation for pressure in a liquid

Answer 9

• Pressure (Pa) = height (m) x density (kg/m3) x gravitational field strength (N/kg)

Question 10

What is upthrust?

Answer 10

• A force that pushes upwards on an object submerged in water
• It is always in the opposite direction to the object’s weight

Question 11

What is the size of upthrust dependent on?

Answer 11

• The density of the fluid
• The volume of fluid displaced
• The greater the density of the liquid, the greater the upthrust will be

Question 12

What causes upthrust?

Answer 12

• The difference in pressure between the top and bottom of the object
• The pressure on the bottom of the object is greater than the pressure on the top of the object

Question 13

How is it decided whether an object will float or sink in a liquid?

Answer 13

• If the upthrust is greater than or equal to the object weight, it will float. Otherwise, it will sink
• If the object is more dense than the liquid it is in, it will sink