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# Weigh yourself on a bathroom scale

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Unformatted text preview: a hanging weight as shown below. The experiment is repeated several times with carts of various masses, using the same hanging weight. (Friction between the cart and the track is so small it can be neglected.) Sketch a qualitatively correct graph of acceleration vs. mass of the cart. (No numbers, just get the shape right.) (3 pts) 8. A 3.0 kg mass hangs from a spring, stretching it from its equilibrium position by 0.10 m. a. Now the 3.0 kg mass is removed and a 9.0 kg mass is hung from the same spring. How much is the spring stretched from its equilibrium position? (3 pts) b. The 9.0 kg mass now hangs from a second spring, and stretches it from its equilibrium position by 0.10 m. Does the second spring have a higher or lower spring constant than the first spring? (2 pts) Name__________________________________ 9. You’re riding a ferris wheel, moving in a vertical circle at a constant speed. The figure shows you at the highest point, moving clockwise (to the right, at the instant shown). Draw a free ­body diagram for your body. Carefully indicate the relative magnitudes of the forces. (4 pts) 10. Cart A, of mass 1.0 kg, travels to the right and collides with cart B, of mass 2.0 kg, initially at rest. The force of cart A on cart B during the collision is shown in the graph at right. a. On the same axes, carefully sketch the force of cart B on cart A during the collision. (Note that the zero of the force axis is 0 in the middle, as marked.) (4 pts) b. The change in momentum of cart B is________ the change in momentum of cart A. (2 pts) i. the same magnitude and the same direction ii. larger magnitude and the same direction iii. smaller magnitude and the same direction iv. the same magnitude and the opposite direction v. larger magnitude and the opposite direction vi. smaller magnitude and the opposite direction 11. A ball that weighs 3.0 N is suspended by two strings as shown. (In the following, get the lengths of the vectors exactly right –– each square represents 1 N of force.) a. On the diagram, draw and label a vector that represents the tension force that string 1 exerts on the ball. (2 pts) String 2 b. On the diagram, draw and label a vector that represents the tension force that string 2 exerts on the ball. (2 pts) String 1 Name__________________________________ 12. Explain how a careful analysis of the motion of a falling ball leads to the conclusion that there must a gravitational force acting on the ball that’s downward and constant. (Be sure to carefully describe the motion, and to use Newton’s laws in your explanation.) (4 pts) 13. Your forearm may be modeled as a uniform rod of length 0.40 m and of weight 15 N, free to pivot about your elbow. Your biceps is connected to your forearm at a point 0.040 m from your elbow, as shown. Determine the force that your biceps must exert to maintain your forearm in equilibrium, at an angle of 30˚ below the horizontal. (8 pts) Fbiceps elbow 30˚ forearm Name__________________________________ 14. Wearing spiked shoes, you pull a box that weighs 400 N along level ice with a 200 N force that’s directed 30° above the horizontal. Friction between the ice and the box is so small it can be neglected. What will be the acceleration of the box? (For full credit your solution must include a correct free ­body diagram, a solution beginning from fundamental equations, proper units, and significant figures.) (12 points)...
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## This note was uploaded on 09/15/2013 for the course PHYS 111 taught by Professor Cui during the Fall '07 term at UMBC.

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