Forces Flashcards
vector
size and direction
scalar
size only
examples of vector
weight
displacement
force
acceleration
velocity
examples of scalars
speed
distance
energy
time
temperature
unit of force
newtons-N
unit for mass
kilograms - KG
unit for weight
newtons - N
or
newtons per kilogram - N/Kg
unit for energy
joules - J
speed =..
distance/time
what does a diagonal ( / ) line mean in a distance time graph
the speed is constant
what does a horizontal ( — ) line mean on a distance time graph
stationary
acceleration =…
(v - u) / t
what does a diagonal ( / ) line mean on a velocity time graph
constant acceleration
what does a straight ( — ) line mean on a velocity time graph
constant speed
how to find distance using a speed time graph
area under the graph
try to split it into triangles and rectangles
area of triangle
(bxh)/2
resultant force
the force leftover from adding two forces
newtons first law
a moving object will continue to move at the same speed and direction unless an external force acts on it
a stationary object will remain stationary unless an external force acts on it
how can an object moving in a circle be accelerating?
the direction is changing, meaning the velocity is changing, so there is a constant acceleration as acceleration is the change in velocity
centripetal force
the resultant force towards the centre of the cirlcle
acceleration is always in the direction of the resultant force
newtons second law
size of acceleration means the size of the force
direction of the acceleration must be the direction of the force
force = ….
mass x acceleration
equation for force using momentum
f=mv-mu/t
how does an airbag save you from large injuries?
increases the time for the human to stop
so there is a longer change of momentum overtime
which reduces the force
equation for impulse
force x time
impulse definition
average force and time of contact for a collision
if force is applied for longer then momentum is…..
greater
newtons third law
If A exerts a force on B, then B exerts an equal but opposite force on A
e.g, I push on a wall, the wall pushes back at me
momentum = …
mass x velocity
efficiency = …
useful energy/total energy
what is meant by closed system?
no outside forces acting on an objetc
thinking distance = …
speed x reaction time
stopping distance = …
thinking distance + breaking distance
when you double the speed, the thinking distance…
doubles
if you double the speed, you quadruple the…
breaking distance
and kinetic energy
this is because breaking distance is linked to kinetic energy and it takes 4 x the distance to remove 4 x the energy
breaking distance
the distance covered to transfer all the kinetic energy of the car to heat energy in the breaks
kinetic energy = …
0.5 x m x v^2
exam style question:
a man falls at a constant speed, as he falls he is losing GPE. Where does that energy go?
since the man is falling at a constant velocity, the energy is most likely transferred into heat energy from friction with air resistance, which dissipates into its surroundings
weight = …
mass x gravity, (10)
what happens to wasted energy
dissipates into its surroundings
what happens to the GPE when an object accelerates downwards
GPE is being transferred to kinetic energy
V^2 - U^2 = …
2 x a x d
GPE = …
mass x gravitational field strength x height
practical question:
why is the ramp slanted during a trolley cart experiment?
this reduces the external forces, friction, from ruining the experiement
practical question:
why can weights only be transferred from the cart to the hanger during the trolley experiment?
the mass cannot change otherwise it would ruin the experiment
explain why the actual speed of an object just before it hits the floor would be different from traditional calculations?
(2 marks)
- some of the energy would be transferred to heat into the surroundings
- so the speed would be less than calculated
Describe one way in which energy is transferred inefficiently when you ride a bicycle
(2 marks)
- friction in the chains will transfer energy into heat
