forces and motion pg 23-25, 32-33, 35-36,40-45

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  • Created by: sophie_kk
  • Created on: 19-11-19 20:50
elastic behaviour
return to their original shape when the forces acting on them are removed
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springs
long coils of wire that can be stretched or compressed by applying a force to them
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uses of springs
absorb raised bumps in the road as suspension springs
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quality of springs
change length when a force acts on them and they return to their original length when the force is removed
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hooke's law
the extension of the spring is proportional to the force
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practical to investigate how the extension of a spring changes with load
length of un-stretched spring is measured with a half-metre rule then the spring is loaded with different weights. the extension for each load is measured against a scale using a set square to improve measurement accuracy .
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practical continued
you will then plot a graph of load against extension, and the extension measurements can be checked by unloading the weights one-at-a-time and remeasuring the extension for each load
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elastic limit
when a spring stops obeying Hooke's law, and starts to stretch more for each increase in load force, and if increased reaches the elastic limit
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what happens to a spring after is reaches elastic limit?
it will not return to its original shape after the load is removed
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do elastic bands obey Hooke's law?
no, when plotted they form a curved line, as the extension is not directly proportional to the force causing it
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force equation
force = mass x acceleration
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how do brakes work?
work by increasing the friction between the rotating wheels and the body of the vehicle
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air resistance
an object moving through air that experiences a force that opposes its movement
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drag coefficient
a measure of how easy an object moves through the air
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how can we produce less air resistance?
give objects a streamlined, smooth surface
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speed and AR
increases as the other increases
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why do falling objects experience?
weight force and opposing drag force
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describe how an object reaches terminal velocity
when an object has just been released the velocity = 0 and so does the drag. When the object begins moving the velocity increases, therefore drag increases as well - at this point the object is accelerating as the opposing force is not as big as the
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terminal velocity cont
as the weight force. However, after some time the object will stop accelerating due to the drag force being equal to the weight force. as there is no unbalanced forces on the object, the objects acceleration is zero therefore it has reached
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cont
terminal velocity, as even though it is still falling the object will not get any faster
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momentum equation
p = m x v
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what is momentum measured in
kg m /s (kilogram metre per second
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increase in momentum eq
mv - mu (final v x m - initial v x m)
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rate of increase of momentum eq
(mv-mu) / t ( also known as force)
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increase in momentum
force x time
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newtons third law
during the time the balls are in contact each exerts a force on the other . they act in opposite reactions and for the same amount of time .
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how does a crumple zone work?
person coming rapidly to a halt - subject to a large deceleration. this means that the mass must be subject to a huge force. the air bag deflates slowly, so time to come to a halt is extended - forces acting on driver during deceleration are reduced
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springs

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long coils of wire that can be stretched or compressed by applying a force to them

Card 3

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uses of springs

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Card 4

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quality of springs

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Card 5

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hooke's law

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