Notesale: Turn your study into money

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- NEWTON’S LAWS OF MOTION –
NEWTON’S FIRST LAW : This law states that every body continues to be in
its state of rest or the state of uniform motion along a straight line unless it
is acted upon by some external force
...
This law helps us to
measure the amount of force
...


Let, ‘m’ be the mass of a moving body, moving along a straight line with an
initial speed ‘u’ After a time interval of ‘t’, the velocity of the body changes to
‘v’ due to the impact of an unbalanced external force F

Initial momentum of the body Pi = mu
Final momentum of the body Pf = mv

Change in momentum Δp = Pf
–Pi
= mv – mu

By Newton’s second law of motion,
Force, F ∝ rate of change of momentum
F ∝ change in momentum / time
F ∝ mv – mu /t
F = km(v – u)/t
Here, k is the proportionality constant
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Hence,
F = m(v – u)/t
Since, acceleration = change in velocity/ time, a=(v-u)/t
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When the net force acting on a body is not equal to zero, then
definitely the velocity of the body will change
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The change may take place either in
magnitude or in direction or in both
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They always act on two different bodies’
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That is, FB = –FA

When a rocket is fired, its fuel is burnt and makes a hot gas come out through
the nozzle of the rocket
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This might be a little complex so, another example is, when birds fly they push
the air downwards with their wings (Action) and the air pushes the bird upwards
(Reaction)

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