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Unformatted text preview: I: Last name initial Winter 2003 Last Name Physics 175 Exam #2 First Name
ID # Points for each question are indicated in parentheses. Show your work for solutions to questions that
require calculations. Explain from where you start to solve the problem and show your math ﬂowing
from it for full credit. Surround your result in a box and don ’t forget to include the units for your result.
If you need more space to ﬁnish a question, write BPP (Back of the Previous Page) at the end of the
space provided and then complete your work on the back of the previous page. For multiple choice
questions, circle the letter which you believe to be correct (or best). In all problems, take the
gravitational acceleration g = 10 m/sz. Problem 1 (5 points) You are pushing a wooden crate across the ﬂoor at constant speed. You decide to turn the crate on end,
reducing by half the surface area in contact with the ﬂoor. In the new orientation, to push the same crate
across the same ﬂoor with the same speed, the force that you apply must be about a) Four times as great :Fowc E 03" (Eva/k 0km &©€r> \Nb‘it‘“ (£61?ng
5 . b) Twice as great
@ Equally great (Dm we: gm C6... d) Half as great
e) Onefourth as great Problem 2 (15 points)
A 1.5 kg block is initially at rest on a horizontal frictionless surface when a horizontal force in the
positive direction of an x axis is applied to the block. The force is given by F (x) = (4 — x2)i in N, where X
is in meters and the initial position of the block is x = 0. a) What is the kinetic energy of the block as it passes through x = 1 m? W2: AK :9) WT“ ky’ggk? 1 b) What is the maximum kinetic energy of the block between X = 0 and X = 3 m? x Aim! Wm: i mam "K .
P 1F; 2 2:, : a wee «A Q Qamli :3 Problem 3 (5 points)
Two cars, starting from rest at the same place, travel by different routes to the same destination. One of
the cars passes the other as they drive through it. Which of the following statements will be true?
a) The work done by friction during the trip was the same for both
b) The total work done on both is the same
@ The work done by gravity is the same on both
d) The work done by gravity on both is positive Problem 4 (26 points)
A stone with mass m = 8 kg is at rest on top of a vertical spring. The spring is compressed 10 cm by the stone.
a) Draw a free body diagram for the system and determine the spring constant, k. “M3? A «a; ﬁawq “*0
to C
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a b) The stone is pushed down an additional 30 cm and then released. What is the elastic potential
energy of the spring just before that release? 1
K UR: 12k ($665; . u :i WW6 c) After being released, what is the speed of the stone when it‘leaves the spring (the spring is at equilibrium)? 2» a EA: 1&3 = a: w: «0+3\ac..&wa;§
inﬁll, Egszi of): 3%; + Wigwam
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v in 6H :i'guﬂé Jr 32 :3 34:: gkﬁzzgl’é d) What is the maximum height that the stone will reach after being released? Wham 3&“3, 5:00.61 \T‘Eiitidxﬁé) V\A..Cx><i um. um Mex: wB : l. \ddﬁdgf EA: EL EN Q. \N
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a» imam; : Wish Problem 5 (5 points)
During the lectures, prof. Kosztin made mistakes. To make up for all the times that she has made a mistake, she decided to give you an easy question, so here it is. What is the ﬁrst letter of her ﬁrst name? @A
D
c) ‘@
d) X e)K Problem 6 (5 points)
A woman runs up a ﬂight of stairs. The gain in her potential energy is U. If she runs up the same ﬂight of stawith twice the speed, what will be her gain in potential energy?
U
b) 2U
c) U/2
d) 4U
e) U/4 Problem 7 (16 points) During the Great Mufﬁn Wars of ’98, students from rival residences became familiar with the
characteristics of various mufﬁns. Mushy Pumpkin Surprise, for example, was good for temporarily
blinding an attacker, while Mrs. O’Brian’s Mufﬁns, having a higher density, were used mainly as a
deterrent. According to the rule,eyery mufﬁn must have a mass of 0.3 kg. During one of the most
memorable battles, a mufﬁn moving to the right at 5 m/s collided with a mufﬁn moving to the left at 2
m/s. Find the ﬁnal velocities of the two mufﬁns if the collision was perfectly inelastic. . ‘ \1‘ pm. t x. Use momma.ka GS \met‘x y jemilmm
if L( (Ft; 2 (Fr mum; Dixxrecliw org “Askew Problem 8 (5 points) 3 An Olympic diver dives off the highdiving platform (point A). The magnitude 1 of his momentum will be a maximum at point C
a) A A
b) B
c) C D W11 Bonus Question (5 points)
A block of wood is struck by a bullet. Is the block more likely to be knocked over if the bullet is metal and embeds itself in the wood, or if the bullet is rubber and bounces off the wood? Explain. The Wale. will lac Wmﬁed ®\r€.\l Al Aim inorle {a \C \ID\/h€\r owl \vawﬁg 0&% We. mood, We dummy,
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 Spring '08
 kozstin
 Physics, Energy, Force, Kinetic Energy, Potential Energy, prof. Kosztin

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