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HW3

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School
University of Illinois, Chicago**We aren't endorsed by this school
Course
PHYS 131
Subject
Physics
Date
Dec 22, 2024
Pages
4
Uploaded by BaronGoose4785
Physics 131 Written Homework Problems: Week 3 | Problem 1: Using free-body diagrams | A. The free-body diagram at right shows the forces acting on a 2.0 kg object. Use Newton’s 2" law to find a, and a,. \ p / 30N VA A y: ()= \ = () i\' 20N \ ¢ YA\ \ \V . : — Y 1LON 40N 7 N 720N iy PO L Y § (T Pes | L \'i z\ Ly - ON ] (/ B. A 50 kg box is pushed to the right along a horizontal, rough surface with a force of 300 N. It accelerates at 4 m/s?. You can assume the drag force is small enough to be neglected. 1. On the diagram at right, draw and label a free-body diagram for the box. 2. Use Newton’s 2" law to find the magnitude of the friction force. O[\J 5 - oy Y ( I Fzm<a) < 50 (\)‘7 =10 ,7*,(,' : A= ‘/'c;“ 4 0 200N= 300N ~ F¢ “Z,0oN ~30Q N e - 300 - F¢ 100N \i/
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Problem 2: Pulling Luggage on a Rough Floor. Consider a woman pulling her luggage (S) hown to the right. Use “E™ for Earth, and * f ( labeling your forces. Include subscripts and superscripts when labeling forces in your FBD. You may drop the superscripts when doing the calculations. Use the usual coordinates (x horizontal, y vertical) S {: 1. Draw a free-body diagram for the suitcase [ ) Determine the x- and y-components of each of the following (G forces (pay attention to signs!) 1 94 5 a. The gravitational force, given that the mass of the suitcase is 12 kg. Fox= 0 Foy = b. Friction from the floor (F), given that the magnitude of the friction force is |Fy| = 10N 7 Fe="10N Fiy = () ¢. Normal force from the floor (F), given that the magnitude of the normal force is |Fy|=110N Fux=1 Fry = o N d. Tension from the strap (S), given that the magnitude of the tension force is |fi7l = 30 N, and that 8 = 30°. / PY RN pe = /‘7132\2 2005 (204 W Y B. Using the components above, compute the x- and y- components of the net force Fyep and Fyt,y. and use these to determine the acceleration components a, and a,. : / FibE = Boli i Nexy Z 1 } IR~ L : C e 3 \iF 1l * } <+~ Fi ' - / | A — f 4 by 4 Tt \)’ ! / J ( 7 ;)! f ! ) T TR DT NI S e ISR T e e B e Sty
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Problem 3: Pushing a Box over a Frictionless Floor I'wo people are moving a box across a floor, as shown in the figure below. The first ties a rope to the box and pulls with a force F,,;;, with a magnitude of 65 N at an angle of 37° from the negative x-axis. The second pushes with a force F,¢,, with a magnitude of 82 N at an angle of 23° from the negative x-axis. The mass of the box is 25 kg, and there is no friction between the block and the floor. . (SN "pull g7e- Y 23° |\, A. On the diagram, draw and label a free-body diagram for the box. Include subscripts and superscripts when labeling forces in your FBD. Make sure the lengths of the vectors representing each force are qualitatively correct. Ay Foull £ s FI\’ Q"'}O ( Rad ) L F 2 F(?vl,-\\ B. Determine the x- and y-components of the forces by the two people, fipu“ and Fpush. pash | Fushe = 805 (19)= - 75t M Youk © Fyushy =145 "k vr.\‘: stv"//bq)\: ’%2‘ Oq ,\/ F,I jhaz 65 N l": = \
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C » -‘,k"/"\ | r\\ "? “ ) D. Use Newton’s 2™ law in the y-direction to determine the magnitude of the normal force exerted on the box by the floor. yf".‘l *Tfl{“-.“{]: = Q0N Fn X —37:04 + D4 (= FN -4, AL )¢ 4 ,) St ; ’2/\\,1 Al = FN Y R) ) J\‘\ i, Determine the magnitude and direction of the acceleration of the box. A FF | L f N : \[’L‘\’X 25 g -shad P i e 4w nek - e ey C = L e =1 lfil _/‘v"uk() / A ~ =5 \O{Y‘ /()/L | 540 ML Yo the \ct
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