Forces and Energy

Strong nuclear force

holds together nucleus of atom, acts over atomic distance

electromagnetic force

between (moving) charges, acts over infinite distance

weak nuclear force

present in nuclear reactions (fission, fusion), acts over atomic distance

gravitational force

acts over infinite distance, the weakest of the 4 fundamental forces

N1L

object will remain at rest/uniform motion in a straight line unless an external force acts on it

inertia

property that causes objects to resist acceleration

equilibrium

state which object is not accelerating

static equilibrium

state which object is at rest

Galileo’s Concept of Inertia

states that without friction, if a ball was rolled on a ramp, it would reach equal height from which it was released and if the ramp was never ending, it would roll forever

N2L

if there is force on a object, it will accelerate

* a is directly proportional to F
* a is inversely proportional to m

N3L

for every action force, theres a reaction force that is opposite and equal, forces always acts in pairs

* opposite in direction
* equal in size and time

why do rxn/axn forces not cancel out?

they act on different objects, only forces acting on the same object cancel out

internal forces

forces that can cancel out if acted on different parts of the same object

static friction

force that prevents an object from starting to move, bigger than kinetic friction

kinetic friction

force that acts when an object is sliding on another

gravitational field strength

a property of the source mass (e.g the Earth), (N/kg)

gravitational force

depends on both the source mass and test mass (e.g, the Earth and the Moon), (N)

relationship between gravitational field strength and distance

inverse square relationship. g @ 1/r^2, r is radius of source mass

1 Joule

1 N \* m

1 Newton

1 kg \* m/s^2 (the force it takes to accelerate 1 kg 1 metre per second)

Watt

1 J/s

power

rate which work is done/energy is transferred

thermal energy

the total kinetic and potential energy in the particles of an object

temperature

average kinetic energy of an objects particles

heat

the transfer of kinetic energy from warmer object to cooler object 7

not net force means

* there are no forces acting on an object
* all forces cancel out

when is work done?

1. force must be applied
2. d>0
3. part of force must be in direction of distance theta cannot = 90

energy

the ability to do work

law of conservation

in an isolated system the total amount of energy never changes

kcal

amount of energy needed to raise the temp of 1 kg of pure water by 1 degree C

kinetic molecule theory of matter

matter is made up of particles that are in constant random motion

thermal energy can be transferred by:

1. conduction- direct contact
2. convection- bulk movement of particles in liquid or gas
3. radiation- electromagnetic waves

latent heat

energy needed for a phase change

specific latent heat

energy needed to change the phase of 1 kg certain matter