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Phys121 M1 2010_Soln

# Phys121 M1 2010_Soln - Phylel/SIO/I—Iassam/Midterm I...

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Unformatted text preview: Phylel/SIO/I—Iassam/Midterm I Name: (write name on every page) Signature: Section Number: Seat Number: 1. Closed Book. Only 1 sheet of paper (double sided) allowed 2. Put ﬁnal answers into the boxes provided. Show essential work next to box. 3. Use reverse sides for scratch work. 4. After you ﬁnish the exam, write and Sign the Honor Pledge in the box below: “I pledge on my honor that l have not given or received any unauthorized assistance on this exam” g = 9.8 m/s.2 Maximum score Actual Score 1 — — 4 5 7 1 — 1 — 2 TOTAL Problem 1 I Last Name: Four balls are thrown straight up from Earth. The ﬁgure is a "snapshot" showing their velocities. They have the same size, but different mass. Air resistance is negligible. Rank in order, from largest to smallest, the magnitudes of the net forces, 200 g Fm 1, Fnetz, Fnct3, Fact 4, acting on the balls. Some may be equal. Give your answer in theforrnA>B=C>D. Sntfs 3 >9 > 27/ 7% my git/mg g 32> ” 7295! M0 Mair?!” 1”” (1L7 / 79” 25 WWI?) Problem 2 A car travels at constant speed along the curved path shown in the ﬁgure below. Five possible vectors are also shown in the ﬁgure; the letter B represents the zero vector. Which vector best represents the car's velocity at position 1? Which vector best represents the car's velocity at position 2? Which vector best represents the car's velocity at position 3? Which vector best represents the car's acceleration at position 1? Which vector best represents the car's acceleration at position 2? Which vector best represents the car's acceleration at position 3? Problem 3 ‘ Last Name: You stand on a spring scale in an elevator sitting on the Earth and measure your weight to be SOON. The same elevator, you are still on it, is now in interstellar space. You are in between two stars, as shown. You are so far away from the stars (and any other masses) that there is no gravitational forces on you. The elevator is moving towards one of the stars, as shown by the arrow in the picture. What is your apparent weight (ie, what does - the scale measure) if (a) you are moving at constant speed upwards at 2 m/s? (b) you are accelerating upwards at 2-sz3—1— 2 57V 144/} 2 O 5791!» 0 star Problem 4 A car traveling at velocity v takes distance d to stop after the br es are applied. What is the stopping distance if the car is initially traveling at velocity ? Assume that the acceleration due t the braking is the same in both cases. 2 V ) i; V) 3/ 4A ﬁx L , V 3 Z 65 4’ (Ed ﬁx Lﬂ/ Viz“ MW» / Problem 5 Last Name: A skier is gliding along at 5.0 m/s on horizontal, frictionless snow. He suddenly starts down a 15° incline. His speed at the bottom is 14 m/s. (a) What is the length of the incline? (b) How long does it take him to reach the bottom? (a) , _ a } W l 0”) géig ~. Mag—2.. Problem 6 Last Name: A 1.0 kg wood block is pressed against a vertical wood wall by a 40 N force as shown in the ﬁgure. Assume there is a kinetic friction force, f, for wood on wood and that the magnitude of f = 0.1*n, where n is the normal force. You are told that the block is sliding and accelerating upward. Find the acceleration upward. or -: Mia/5”?“ 5?” KW I‘M/S" 7% SM ' £53 m/{l WM 74 “aw/40 _ ' K0 @530 :7!” W3 Problem 7 Consider the system shown in Mass of A = 1kg, mass of B =j . There \/ is friction between A and the table, f = Mn, where mu = 0.5 and n is the normal force. Find the acceleration of mass B. Last Name: String The tension in the string is the same on both sides .. ‘ of the pulley. Massless, a k.” frictionless ...
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