Physics CT2 Flashcards
Define resultant force
overall force on an object
define balanced forces
‘cancel’ each other out, giving a resultant force of zero
define newton’s first law
an object will only accelerate if there is a non-zero resultant force acting on it
when does newtons first law only work
when there are balanced forces
what will happen to the object if it is already moving and the speeding up force and slowing down force are balanced
the object would still move at a constant speed
define mass
a measure of how much matter there is in an object
what is mass measured in
kg
is mass a vector or scalar
scalar
define weight
a force, which has the mass and the gravitational field strength
what is weight measured in
N
is weight vector or scalar
vector
how to calculate weight
mass x gravity
define terminal velocity
the weight of a falling object is balanced at terminal velocity by the drag force/air resistance
What is newton’s second law
if there are no forces acting on an object, it won’t accelerate
how to calculate the force
mass x acceleration
What happens to the acceleration if the mass increases
it will decrease
define inertial mass
the more mass an object has, the more force is needed to accelerate it
what are scales called in science
balances
what is newtons third law
when two objects interact, there is always a pair of forces present, know as action-reaction forces
What are action-reaction forces
always the same size and in opposite directions
How to calculate efficiency
useful energy out / total energy in
define thermal conductivity
is a measure of how well a material transfers energy
what is an example of a high thermal conductivity
Metals - copper
what does it mean when an object has a high thermal conductivity
heat travels through it quickly
what is an example of a low thermal conductivity
Insulators - plastic/rubber - and still air
what does it mean when an object has a low thermal conductivity
heat travels through it slowly
what are the 3 heat transfer mechanisms
-conduction
-convection
-radiation
define conduction as a heat transfer mechanism
heat energy moves through the material. vibrating particles in a material pass their energy to their neighbour particles
define convection as a heat transfer mechanism
warm fluid rises above colder fluid. The hot fluid moves somewhere else, taking the thermal energy with it
define infrared radiation as a heat transfer mechanism
thermal energy is transferred by infrared light. it is the only method that works in a vacum
what does infrared mean
before what we can see with our eyes
define gravitational potential energy
it depends on the objects mass and height above the ground
How to calculate the change in gravitational potential energy
mass x gravity x change in hight
define kinetic energy
it depends on an objects speed and mass
How to calculate the kinetic energy?
1/2 x m x v(squared)
how many grams in a kg
1000
what does it mean when energy is conserved
kept the same
what unit is gravitation potential energy given in
J
How many newtons are in a kN
1000 n
