Pressure, Gravity and Moments

Question 1

Density

Answer 1

The density of a substance is its mass per unit volume

Question 2

Unit of density

Answer 2

The unit of density is the kilogram per cubic metre

kg / m*3

Question 3

Pressure

Answer 3

Pressure is the force per unit area

Question 4

Unit of pressure

Answer 4

The unit of pressure is the pascal (Pa)
1 pascal = 1 newton per square metre
i.e. 1 Pa = 1 N / m*2

Question 5

Archimedes’ principle

Answer 5

States that when an object is partially or completely immersed in a fluid it experiences an upthrust equal in magnitude to the weight of the fluid displaced

Question 6

The law of flotation

Answer 6

States that the weight of a floating body is equal to the weight of the fluid it displaces

Question 7

Boyle’s law

Answer 7

States that at constant temperature the volume of a fixed mass of gas is inversely proportional to its pressure

Question 8

Newton’s law of universal gravitation

Answer 8

States that any two point masses in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them

Question 9

Moment of a force

Answer 9

The moment of a force about an axis is equal to the magnitude of the force multiplied by the perpendicular distance from the axis to the line of action of the force
i.e. moment of force = force x perpendicular distance

Question 10

If a body is in equilibrium then:

Answer 10

The vector sum of the forces in any direction is zero

The sum of the moments about any point is zero

Question 11

Couple

Answer 11

Two parallel forces with the same magnitude acting in opposite directions is called a couple