physics mechanics

theory only

what is a scalar quantity

anything with size but no direction

what is a vector quantity

anything with both size and direction

what is speed

rate of change of distance

what is displacement

a distance in a given direction

what is velocity

the rate of change of dispalcement with respect to time

what is constant velocity

a velocity that does not speed up or slow down

what is acceleration

the rate of change of velocity with respect to time

what is a force

a force is anything that causes the velocity of an object to change 

SI unit - newton(N)

what is a newton

1 newton is the force that gives 1kg an acceleration 1m/s²

what is weight

the force due to gravity

w=mg

what is gravity

the force that attracts a body towards the centre of the earth, or towards any other physical body having mass.

what is momentum

momentum is mass x velocity

p=mv

SI unit is KG m/s

what is newtons first law of motion

every body will remain in a state of rest or travelling at a constant velocity unless an unbalanced external force acts on it

newtons second law of motion

when an unbalanced external force acts on a body the rate of change of the body’s momentum is dircetly proportional to the force and takes place in the direction of the force

newtons third law of motion

Every action has an equal and opposite reaction

what is friction

friction is a force that opposes one surface sliding along another

what is terminal velocity

when the weight is equal to the air resistance and falls at a constant velocity it has reached terminal velocity

principle of conservation of momentum

the total momentum of two bodies before an interaction is equal to the total momentum after the interaction provided no external forces act  on the system of bodies

momentum before collision = momentum after collision

what is density

mass per unit volume

pressure

force per unit area

P=F/A

force per unit area

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 lliquid or gas

what is archimedes principle

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

what is boyles law

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

PV=k

what is newtons law of universal gravitation

newtons law of universal gravitation states that any two point masses in the universe attract each othr with a force that is 

1. directly proportional to the product of their masses

2. inversely proportional 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 mutiplied by the perpindicular distance from the axis to the line of action of the force 

M=FxD

SI unit is a newton metre (Nm)

when will a body be in equilibrium

1. the vector sum of the forces in any direction is zero (forces up=forces down)

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

what is work

force by distance

W=Fs

SI unit is a joule (J)

What is energy

the ability to do work

kinetic energy

energy a body has due to its motion

E_k=1/2mv²

what is potential energy

E_p=mgh

what is the principle of conservation of energy

it states that energy cannot be created nor destroyed but can only be converted from one form to another

what is power

power is the rate at which work is done/energy is transferred