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X3.6d

PHYS-205(6) (Kaldon-40534)

Name ______________________________________________

Exam 3 - 100,000 points + 20,000WMU-Fall 2000

(^)
(^) points

11/16/2000•Rev.

State Any Assumptions You Need To Make – Show All Work – Circle Any Final Answers Use Your Time Wisely – Work on What You Can – Be Sure to Write Down Equations

Feel Free to Ask Any Questions

2a

2b

2c

2e

“And Now We Take You To Palm Beach County, Florida…”

(50,000 points)

machine. Each card ( 1.) (a) Suppose you suddenly have 400,000 computer punch card ballots to run through a counting

(^) m = 0.000454 kg

(^) ) has to move 20.0 cm (0.200 m) in 1.00 seconds. A spinning

drive wheel of 6.00 cm diameter (0.0600 m) moves the cards along. Find the angular velocity,

, of the

drive wheel.(b) The solid drive wheel has a mass of 50.0 grams (0.0500 kg). Find the rotational kinetic energy of thedrive wheel.

(^) If you did not get an answer to (a), use

(^) = 20.0 rad/sec

.

(c) Suddenly a card jams in the machine and the system automatically stops. Find the angular acceleration to bring the drive wheel to a stop in a single rotation.

(^) If you did not get an answer to (a), use

(^0) = 20.

rad/sec

.

Physics 205 / Exam 3

Fall 2000

Page 2

(d) One of the problems with the ballots in parts of Florida is

(^) chads

(^) – the small bits of the cards that are

this is a tension force problem, withas shown in the illustration – let us assume thata region of the card, you may stretch the materialsupposed to be punched out. If you just push on

T = 10.0 N

.

Consider a card that is

0.100 mm = 0.000100 m

L thick, where the size of the stretched region is 0 = 2.00 mm = 0.00200 m

(^) and

(^) 2.00 L

0 deep.

The material is depressed by

(^) d = 0.250 mm =

0.000250 m

. Find the Young’s Modulus,

Y

m (^) , of the card material.

(e) A U.S. flag hangs from a bracket wall. The flag and pole provide a positive torque,



(^) = 30.0 N ·m

,

flagpole is appliedabout a pivot point at the end of the bracket. To keep the flag from falling, a force perpendicular to the

(^) 7.00 cm

(^) from the pivot point. Determine if this force is F

(^1) or F

(^2) , and then find the

magnitude of this force.

Physics 205 / Exam 3

Fall 2000

Page 3

So You Think You’ve Got Star Problems? When I Was A Kid…

(50,000 points)

2.)

(a) A plate of mass m = 6.00 kg has dimensions a = 1.50 m and b = 0.720 m.

Find the center of mass coordinate

(^) x cm (^) by integrating

(^) x

M

x dm

cm (^)

z

.

(b) A plate of mass m = 6.00 kg has dimensions a = 1.50 m and b = 0.720 m.

Find the moment of inertia

I

(^) of the plate about an axis along the left edge as shown,

by integrating

I

r dm

z^

(^2)

.

Physics 205 / Exam 3

Fall 2000

Page 4

(c) A simple harmonic oscillator has an acceleration given as

(^) a t

m s

t

( )

.

/

cos(

)

(^2)

b

g

. Find

(^) x(t).

M (d) Bob weighs 981 N on the surface of the Earth. What would his weight be on the planet Mercury? M (^) = 3.18 × 10

(^23) kg , R^

M (^) = 2.43× 10

(^6) m , g = 9.81 m/s² , G = 6.67 × 10^

- N·m²/kg²^

.

(e) A torque

to tighten a bolt consists of a force being applied at a distance from the axis of rotation.

given byAs the bolt gets tighter, it gets harder and harder to turn the bolt, so the torque as a function of angle is



C

, where C is some constant with appropriate units. If the total work done by applying

this torque through two complete revolutions is 1500. J, then find C.