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Homework uestions from sheetIn both thesequestionsthe key is constant8 whichmeans EE whichmeans lefties righties andapples downiesDraw the forcediagram The weight isFogwe will use F for the applied force Since isconstant we know there must be equalforcesup down and leftfright Theupward forceis thenormal force and the force opposingthe motionIfrikhI 4N
7 60ON
11
Since EFItg 600N
F F 60 on f MN youcan't
N IF 600N reforget this
µ fizzixisfun60thGOON 0 too
there are nounits tou itis a ratio of2 forces
2 gqy.E.gs5
500NThe first thing is we must realizepullingup at an angle is likepulling in 2 directionsat the same time we break F intohorizontal and vertical components Fxand Fy using trig below Since u asconstant again EFLefties righties uppies dowries
f Fx Faso NtFy Fg50.0N cos30 Ntfs in 30_Fg
a 43 3N Nt 50sin38 500Nc N 425N
d f MNµ 44
34 0.0912g
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So what if EF This iswhere Newton made a real breakthroughNewton's 2nd Law
K math terms this is a EIm
A direct proportion Ad EFmeans if we plot a vs IF it looks
like this
Whereas an inverse proportion A Atmlooks like this
I
In reality Newton recognized that ferag.ve obgeet
th EFa
constantwhich is how we define inertialmasy
How hard it is to change what an objectisdoing How hard EF change a
We usually remember this equationin linear form
EF a
Newton's 2nd Law
This one is worthy of an equationsheet
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In the example below µ so thereis no friction Because the object ison the floor there is a normal forceObviously the object is accelerating to theright
TN Ef y
f x
In the y dir In X derEF Cno a iny dir EF F ma
N Fg COON 20N ma
But what is mWe know from our discussion of mass and weightthat Fg omg 20 10.2kgCa
m nyg a 1.96Mls's
Ig70.2
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Now add frictionc Draw in the forces2 WriteNewton'sLawsequations in the
x and y directions3 Use f µN to find f4 Solve for a
f TN
LtgKir Ca x dir CatN Fg EE F f ma
mg106807
50
syr yaa
f MN to 29198N0kg
245N 2.5545c
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