2.6 Analysing Impulse & Impulsive Force
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Transcript of 2.6 Analysing Impulse & Impulsive Force
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2.6 Analying impulse and2.6 Analying impulse and
impulsive forceimpulsive force
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Learning Outcome :Learning Outcome : Explain what an impulsive force is.Explain what an impulsive force is.
Give examples of situation involvingGive examples of situation involvingimpulsive forces.impulsive forces.
efine impulse as a change of momentum!efine impulse as a change of momentum!
i.ei.e "t # mv $ mu"t # mv $ mu
efine impulsive force as the rate of changeefine impulsive force as the rate of changeof momentum in collision or explosion i.eof momentum in collision or explosion i.e
" # mv $ mu" # mv $ mu
tt
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Learning Outcome :Learning Outcome :
Explain the effect of increasing orExplain the effect of increasing or
decreasing time of impact on magnitude ofdecreasing time of impact on magnitude of
the impulsive forces.the impulsive forces.
escri%e situation where an impulsiveescri%e situation where an impulsive
force needs to %e reduced and suggestforce needs to %e reduced and suggest
ways to reduce it.ways to reduce it.
escri%e situation where an impulsiveescri%e situation where an impulsive
force is %eneficialforce is %eneficial
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"ormula of &mpulse"ormula of &mpulse
&mpulse is the product of force and time&mpulse is the product of force and time &mpulse experience %y the %all&mpulse experience %y the %all
&mpulse # "t&mpulse # "t
&mpulse # momentum change&mpulse # momentum change
# mv $ mu# mv $ mu
'nit : (gms)* or +s'nit : (gms)* or +s
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600kg600kgA car of mass is movingA car of mass is moving
with velocity of . A netwith velocity of . A net
force of is applied on theforce of is applied on thecar for . "ind the impulsecar for . "ind the impulse
exerted on the car and henceexerted on the car and hencedetermine the final velocity ofdetermine the final velocity of
the car.the car.
15s15s
200N200N
30m/s30m/s
Example * :Example * :
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Answer:
&mpulse # " t# ,2-- ,*/
# 0---+s
&mpulse # mv ) mu ,0--- # 6--v ) 6--,0-
6--v # 0--- 1 *---
v # 2*---36--# 0/ m3s
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4hat is impulsive force54hat is impulsive force5
&mpulsive force is defined as the&mpulsive force is defined as the
rate of change of momentum in arate of change of momentum in a
reaction.reaction.
&t is a force which acts on an&t is a force which acts on an
o%ect for a very short intervalo%ect for a very short interval
during a collision or explosion.during a collision or explosion.
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An &mpulsive "orce is 7eneficialAn &mpulsive "orce is 7eneficial
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Example 2:Example 2:
A car of mass *---8g istraveling with a
velocity of 2/ m3s. 9he car
hits a street lamp and is
stopped in -.-/ seconds.
4hat is the impulsive forceacting on the car during
the crash5
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Answer :Answer :
&mpulsive "orce :&mpulsive "orce :
" # m,v)u" # m,v)u
tt
# *---, - $ 2/ # *---, - $ 2/
-.-/-.-/ # ) /--!---+# ) /--!---+
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Effect of time on impulsive forceEffect of time on impulsive force
* : Long ump* : Long ump 9he long ump pit is filled9he long ump pit is filled
with sand to increase thewith sand to increase the
reaction time whenreaction time when
athlete land on it.athlete land on it. 9his is to reduce the9his is to reduce the
impulsive force acts onimpulsive force acts on
the leg of the athletethe leg of the athlete
%ecause impulsive force%ecause impulsive forceis inversely proportionalis inversely proportional
to the reaction time.to the reaction time.
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Effect of 9ime on &mpulsiveEffect of 9ime on &mpulsive
"orce 2 : ;igh ump"orce 2 : ;igh ump uring a high ump! auring a high ump! a
high umper will land onhigh umper will land on
a thic8! soft mattressa thic8! soft mattress
after the ump.after the ump. 9his is to increase the9his is to increase the
reaction time andreaction time and
hence reduces thehence reduces the
impulsive force actingimpulsive force acting
on the high umper.on the high umper.