# Forces

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- Created by: vickieboadi
- Created on: 08-05-18 07:41

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

it is by the gradient

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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

#### Front

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

#### Back

### Card 4

#### Front

what is a contact force

#### Back

### Card 5

#### Front

what is a resultant force

#### Back

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