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Unformatted text preview: ' 4.2 ' ' The acceleration given to the footmd from ”—1; 7304 arias7 V'V 10m/ 
a'_"E—Q"—fﬁois_q"5°m/32 Then. from Newton's 2“‘1 Law, we ﬁndF— ma _ (o .50 kg)(50 W32), 25 N. 67. ,, .._..J _... _. 4.8 (a) We resolve the forces shown mto
‘  F =400N FR: 122'N 789 N
The magnitude of the resultant force is found from the orean theoremas FR (m)2 + (zpyﬂ (122 m2} (789 mil7933:, and tansQ 131392;  6.47, fromwhinh 9 812“. Thus, the resul
umt force is at an angle of 8.8“ to the right of the forward direction. (13) The acceleration is in the same direction as PR and is given_by
_ arVﬁ/m= 798‘NQ99932,:9;6_6_§113?: _. , _ , , __.__H.__h__,_,,__,,___h ,. _;__;, ____..
4.15 (a) A study of the forces on the block that are
parallel to the incline reveals that
mFcosa mgsine0,so n F  (2.0 kg)(9.80):‘o‘;2g.  33.9 N. (34 N) ZFyN Bins  mgcossO, sothat
N Fsinﬁ + mgcose  (33.9 N}sin60° + (2 ¥_w__..,,,,, _. _ W," _ 4.20 mum m 1 . _
haveg 1 00kgandm2 5.00kg,we
1 mlamlgV—V'I:
£1123  T ngsine.
Adding these gives
("11 + Ema11113  ngsine. Thus, ”(W g,“ m1 '+ mg
10.0  5.00 sin40‘
3" ( 15 ) 9.80  4.43 m/sZ. [Taina {g \m .
1'11 Inn nf a owes: T m1 (5!  a)  10.0(930  4.43) = 53.7 N. 4.28 First, consider the 3.00 kg rising mass. The '
forces on it are the tension, T, and its
weight. 29.4 N. With the upward direcﬁon as positive, the second law becomes
T— 29.4. N  (3.00 kg)a. TheforcesonthefaﬂingSDOkgmassare its weight and T, and its acceleration is the
sameasthatoftherisingmass. Caiiingthe
positive direction down for this mass. gives 49 N  T: {5.00 kg) a. (a) the tension as T 36.81% (b) and the acceleration as
(c) Consider the 3.00 kg mass We have 4.32 (a) a v;  vg_ 6.00 m/s
t We also know that Nmg. Now app
f= m(1.20 m/sz) 01'
But, also, 1"  pkN = pkmg. (1) (2) a  2.45 m/sz. y= Vot+%at2 0». i— (2.45 m/s2)(1.oo s)2 —123 m. + Equations (1) and (2) can besohred simultaneously to give 53110 m/ ..120 111/32. lythesecondlaW! fm(l.20 111/52). (1)
From (1) above, we have . 2 'pknig m(1.20 m/sz) , so Pk‘ 930 “1/3: (c) x {r r (9——~) t (Wysm s)  45.0 m. V+Vf
2 ...
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 Fall '01
 Shapiro
 Physics

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