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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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