physics-pressure,gravity and moments

chapter 10

what is density?

The mass per unit volume of a substance

m/v

what is pressure

the force per unit area

F/A

what is pressure in a liquid

P=pgh

what is upthrust

if an object is immersed in a liquid or gas there is an upward force acting on it due to the liquid or gas . This force is called the upthrust or the buoyency force

what is archimdes principle

when an object is immersed in a fluid it experiences an upthrust that is equal in size to the weight of the fluid it displaces

what is the law of flotation?

the weight of a floating body is equal too the weight of the fluid it displaces

what is boyles law

for a fixed mass of gas at constant temperature,the volume is inversely proportionate to the pressure at a constant temperature

what is newtons law of universal gravitation?

any two point masses in the universe ttract each other witha force that is

1. directlly proportional to the product of their masses

2. inversely proportionate to the square of the distance between them.

what is a moment of a force?

the moment of a force about an axis is equal to the magnitude of the force multiplied by the perpindiculardistance from the axis to the line of action of the force

M=Fd

what is an equilibrium

a body will be in equillibrium if 

1. the vector sum of the forces in any direction is zero

2. the sum of the moments about any point is zero

what is a couple?

two parallel forces with the same magnitude acting in opposite directions