# Forces

what is a scalar
scalars only have magnituge - e.g. tempreture, distance, speed, time, mass
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what is a vector
vectors have magnitude and direction- e.g. displacment, velocity, acceleration, momentum
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what is a non-contact force
when the objects are physically separated - e.g. magnetic, gravitational
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what is a contact force
when the objects are physically touching - e.g. friction, air resistance
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what is a resultant force
when 2 or more forces are acting on an object, the motion of the objects depends on a the combination of all these forces. the combination of the forces is called the resultant, it can be thought to be a single force that could replace a forcesactin
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what is mass
mass is the amount of matter in an object
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what is weight
weight is the force acting on an object due to gravity, the force of gravity depends on the gravitational field around the earth
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what us the equation for weight
weight = mass x gravitational field strength
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what is workdone
this is when a force move an object and when energy is transferred and work is done
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what is the equation for work done
work done = force x distance moved in the direction of the force
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what does hooks law state
it states that the extension of the a spring is directly proportional to the load, provided the limit of proportionality has been exceeded
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what is the equation for force
force = spring constant x extension
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what is the equation for elastic potential
elastic potential energy = 0.5 x spring constant x extension2 (1/2ke2)
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what happens if an object has defrmed elastically
it means the amoun of work done on it is equal to the amount of elastic potential energy which has been stored in it
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what is the equation fore moment of force
moment of force = force x distance (M=Fd)
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what happens if an object is balanced
anticlockwise moments = clockwise moments (f1 d1 = f2 d2)
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what is the equation for pressure
pressure = force/area
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what is the equation for pressure in a fluid
pressure = height of the column x density of the liquid x gravitational field strength (p=hpg)
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what is the equation for speed
speed = distance/ time
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what is the equation for average speed for a journey
average speed = total distance/ total time
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what is the equation for acceleration
acceleration = change in velocity/ time
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what is the equation for resultant force
resultant force = mass x acceleration
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what is newtons first law
if the resultant force acting on an object is zero, then its accelaration will be zero
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what is the equation for stopping distance
stopping distance = thinking distance + braking distance
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what is the equation for momentum
momentum = mass x velocity (p= mv)
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what does force equal
force = rate of change of momentum
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how do we make thigns turn from the pivot
if we exert a force further away from the pivot the moment exerted increases
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what is the priciple of moments
when the object is at an equlibrium the sum of the anti-clockwise momets about the pivot is equal to the sum of the colckwise moments
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what do levers allow
they allow the rotational effects of a force to be transmitted from one object to another
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what do gears allow
they allow the rotaional effect of a force to be increased or decreased
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eqaution for using gears to increase the rotational effect
input: m1 = f x r output: m2 = f x 2r - increasiong the radius of the gear doubles the moment or the turning force
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why does atmospheric pressure decrease with height
air pressure is caused by the force exerted when moving ari particles collide with a surface,
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why does atmospheric pressure decrease with height
as the height icreases, the density of the air decrases, which means that air particles collide into objects and other air particles less frequently
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equation for distance
s = vt (distance = average speed x time )
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how is the speed calculated from a distance time graph
the speed of an object can be claculated from the gradient of its distance time -graph
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how do you measure the speed from an object which is accelarating from a distance time graph
you draw a tangent to the line at that time measure the gradient
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accelaration equation (2)
v2 -u2 = 2 as
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how do work ou the accelartion of an object froma velocity time graph
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hwo do you calculate the distane travelled by an object
this is by the area underneath it velocity -time graph
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newtons second law
an object will accelarate if there is a resultant force acting on it the accelaration of this object is propertional to the rf and inversley proportional to it mass f = ma
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newtons third law
when one object exerts a force on another, the second object will exert an equal an opposite force on the first
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inertia
the greater the inertial mass of an object the more difficult it is to change it velocity ( a=f/m)
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what fators affect reaction time
tiredness, distractions, alcohol consumption and drugs
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what factors affect the braking distance
condition of its brakes and tyres, type os road surface, weather conditions and size of the breaking force
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what happens to momentum in a closed system
the total momentum before any event is the same after any event
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eqaution for momentum 2
force = mass x change in velocity / change in time
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## Other cards in this set

### Card 2

what is a vector

#### Back

vectors have magnitude and direction- e.g. displacment, velocity, acceleration, momentum

### Card 3

#### Front

what is a non-contact force

### Card 4

#### Front

what is a contact force

### Card 5

#### Front

what is a resultant force