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Phys115F07Exam1Key

# Phys115F07Exam1Key - Name K ‘ei Phys.115 Exam I 26...

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Unformatted text preview: Name: K ‘ei/ Phys.115 Exam I 26 September 2007 Please do not turn the page until you are told to do so. Make sure that you have all three problems on your copy of the test. In order to get credit on a problem, you must show your work. If you only write down an answer without the work leading up to it, you will get no credit for it, even if it is the right answer. 1) A hot—air balloon carrying a basket is descending at a constant velocity of 20.0 m/s. A person in the basket throws a stone with an initial velocity of 15.0 m/s horizontally, perpendicular to the path of the descending balloon. 4.00 3 later, this person sees the rock strike the ground. (a) (7 points) How high was the balloon when the rock was thrown out? Vabaﬂiesw 1’ it m“ L ; 3 ‘ I 3‘ i Whoa 4" 4’07 x + *7? Q7 f C? "r 2" it +’/’02’0"g 0635/) all]: "?(¥M/J‘)/£WQO 1/)L (b) (6 points) How far horizontally does the rock travel before it hits the ground? W : ﬁx :0 it; 3% :, (Maia “0/5 M W“) “:1; éQ’OW‘ :2) x a (c) (7 oints) At the instant the rock hits the ground, what is the total distance etween the rock and the basket? P t . t 7 Whody 3g {plane-roe cast 4%; (amalgam, frag/gr ( (1+ wnxi . (weed m \$0635 , 1 a MA? :44 I #16903) mom i) £13, a: ﬁ [5.8% 690' gm 0; yﬂo’o m grout/cad Wham 756 rack My 4m TQM- Probleml - \ ft Z \EX1+71 : ml W Momma“; e (if; ,0 m) + m m) 2) While a fractured tibia (the larger of the two major lower leg bones in mammals) is healing, it must be held horizontally and kept under some tension, so that the bones heal properly. One way to do this is to support the leg by using a variation of the Russell traction apparatus. The lower leg, including the foot, of a particular patient weighs 51.5 N, all of which must be supported by the traction apparatus. (a) (10 points) What must be the mass of W, shown in the figure? Assume that the sling around the leg is slack, so it does not provide any force. ’ 3:6 =0 ‘72.}, as v ma w 7m 3? «m ' 51.5/d ma Maw w ‘M\ ' T: \$1M» «Si/157% a“ rinqamjm 3} T: w‘: 43w x I , M 2 ‘ ; arm/f t... (b) (10 points) What traction force does the apparatus provide along the direction of the leg? “2;: v.» Tm 3% "rm 4‘6 #EJA/cwil? +mw) K )W 3) The 4.00 kg block in the figure is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown in the figure. The tension in the upper string is 80.0 N. (a) (6 points) Draw a free—body diagram of the block. (,09 W... . , ~t : :7 31/ {71> 25m Mlpgf (b) (7 points) What is the tension in the lower string? :6, \$0 Tusfné‘w M; “723509”? > § 7 .Vm/J‘L r - [LOO/z" (I? W“): 3’0” TL 2 -— M 5731" 7 " Sai’t Q (c) (7 points) What is the speed of the block? 'L WWW ,. ZR '= m .1“:— 21: \jﬁﬂé‘mil" (l-MMY Lagsom /L "L . a . a ’17 TL 09! e; + “Tu cm 9 m If" M ##H ’1)”: -Wm)w59 >\W+3iom)w m .4 X y Z A t9=tan_1——y AX # A? 122—— At a A?) a:— At 1 2 x=x0+v0t+——at 2 v=v0+at v2=v§+2an 213=mc7 Fszlnj2 R kaﬂkFN 2 v ac:— r 27zr T:— v 2 Fczmv r constants g=9.8m/S2 G = 6.67 ><10‘“Nm2 /kg2 ...
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