physics Flashcards
average speed =
distance moved / time taken
acceleration =
change in velocity / time taken
force =
mass x acceleration
weight =
mass x g
momentum =
mass x velocity
moment =
change in momentum / time taken
Q(charge) =
I x t (current x time)
E (energy) =
Q x V (current x voltage)
V (voltage) =
I x R (current x resistance)
P (power) =
I x V (current x voltage)
wave speed =
frequency x wavelength
n (refractive index) =
sin i / sin r
sin c (sin of critical angle) =
1 / n (refractive index)
Effeciency =
useful energy output / tutal energy output
what does it mean if the line is steep on a distance time graph
the greater the steepness the greater the speed of the object
examples of forces
weight
lift
electrostatic
tension
friction
thrust
magnestic
drag
contact
upthrust
what is a resultant force (and how do you calculate it)
if more than one force acts on an object you have to calculate the resultant force
(bigger force - smaller force = resultant force)
AND SAY THE DIRECTION
what happens if the resulant force is in the same direction as the object
the object will accelerate
what happens if the resultant force is in the opposite direction to the object
the object will decelerate
what happens if the resultant force is zero
the object will be stationary or moving at a contant speed
what is terminal velocity
The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces.
what is a scalar
a quantity that just has a size
what is a vector
a quantity which has size and direction
How can we tell Hooke’s law on a graph
on a force extension graph is the line is straight through 0 then the object is obeying the law
what does it mean if an object has elasticity
the object returns to its original shape after the force is removed
which part of a velocity time graph can be used to calculate distance travvled
the area under the graph
what are ways that force can affect the object that it is being applied on
change in shape
change in speed
change in direction
what is the equation between
stopping distance
breaking distance
thinking distance
of a car while it is stopping
stopping distance = thinking distance + breaking distance
what is the thinking distance
the distance the vehicle travels in the time it takes for th driver to apply the breaks after realising they need to stop
what are things that affect thinking distance
drugs, alcohol, distractions and tiredness
what is breaking distnace
the distance that an object travels from the time when the breaks are applied to the time when it comes to a complete stop
what factors affect breaking distance
speed of the vehicle, road conditions, weight of the vehicle, and slippery roads
what are safety features in roads
roundabouts
narrow lanes
speed bumps
traffic lights
stop signs
speed limits
what are safety features in cars
airbags
seatbelts
cruise control
headlights
breaklights
parking sound assists
what are many injuries in vehicle collisions and sporting injuries due to
the rapid acceleration of the body (they stop very quickly)
what can you do to the momentum to help improve the injury
by spreading the change in momentum over a longer time it recudes the force required to act which reduces the injury
explain how the seatbelt protects
it stretches so it increases the time to come to a stop
explain how a crumple zone protects
parts of the car are desgined to collapse so the car takes longer to stop moving
what is the conservation of momentum
total momentum before = total momentum after
what is newtons 3rd law
when objects are touching they exert equal and opposite forces on eachother
what is a lever
an object rotating or trying to rotate
what is a pivot
the point around which the lever is rotating or trying to rotate
what is a moment
the size of the turning effect of a force about a pivot
what is the principle of moments
clockwise moment = anticlockwise moment
what is the centre of gravity
the point in an object where all of the wright appears to act
how do you find the centre of gravity
if an object is placed such that it’s centre of gracity is on top of a pivot, the object will be balanced
why will the object be balanced when you find its centre of gravity
the perpendicular distance between theweight of the object and the pivot will be zero
