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PHY111 Exam 2
Evening Version
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Part I: Multiple-Choice Questions.
10/25/00
MacIsaac
Page 1
SID#:
These questions are worth 3 points each, and will be scored by the partial-credit scheme (correct answer in one
response = 3 pts, correct in 2 responses = 2 pts, correct in 3 = 1 pt). Please clearly mark your responses on
this page. Choose the BEST answer.
1. A coin is stationary on a wooden board. One side of the board is slowly raised until the coin begins to slide
down the incline. If the angle between the board and the horizontal is 33˚, what is the coefficient of static
friction between the coin and the wooden surface?
A. 0.54
B. 0.84
C. 0.65
D. 0.74
2. An elevator weighing 10,000 N is supported by a steel cable. Determine the tension in the cable when the
elevator is accelerated upward at 3.0 m/s2.
A. 7.0 x 103 N
B. 10,000 N
C. 111 x 104 N
D. 1.3 x 104 N
3. A car traveling 20 m/s rounds an 80-m radius horizontal curve with the tires on the verge of slipping. How
fast can this car round a second curve, of radius 320 m? Assume that the coefficient of friction stays constant.
A. 40 m/s
B. 30 m/s
C. 80 m/s
D. 50 m/s
4. A car of mass M is going around a banked curve ( = 7˚ with respect to the horizontal). In a free body
diagram reflecting this situation which force component equals the centripetal force?
A. Mg Sin
B. Mg
C. FN Cos 
D. FN Sin 
5. In a galaxy far, far away, two planets (Zorg and Endor) orbit the same star. Planet Zorg orbits the star in
300 days (2.59 x107 seconds) at a radius of 1.3 x1011 m. Planet Endor orbits at a radius of 2.7x1011 m. How
long is a year on Endor?
A. 6.0 x 107 sec
B. 5.2 x 1014 sec
C. 7.75 x 107 sec
D. 2.4 x 108 sec
PHY111 Exam 2
Evening Version
10/25/00
MacIsaac
Page 2
Part II: Short Answer Questions.
These questions are worth 3 points each, and require both units and reasonably significant figures. Partial
credit may be awarded for work shown. Choose the BEST answer.
6. Two forces are acting on a 5 kg block. F1 has a magnitude of 45 N and is pushes from 65 degrees above the
negative x axis. F2 has a magnitude of 25 N and pushes towards the negative x axis (directly left). What is the
resultant acceleration vector (size and direction)?
7. The gravitational acceleration gmoon on the moon is 1/6th of the g on earth. If an object weighs 98 N on the
earth what is its mass on the moon?
8. Your younger brother (mass 20 kg) is sitting on a snow sled (weight 29.4 N). You push him on level ground
with of force of 50 N, at an angle of 40˚above the x axis. The coefficient of kinetic friction between the sled
and the snow is 0.10 What frictional force exists between the sled and the snow?
9. A food processor has been turned on, and the Frappe button has been pressed. A blade of length 0.055m
makes one complete revolution in 0.008 seconds. What centripetal acceleration is the tip of the blade
experiencing?
10. On Uranus, the value of surface gravity is 9.21 N/kg. The radius of Uranus is
2.51 x 107 m. What is the mass of Uranus?
PHY111 Exam 2
Evening Version
10/25/00
Part III: Problem-Solving & Discussion Questions.
MacIsaac
Page 3
These questions are worth 5 points each, and all require a diagram and explanation in clear phrases or point
form. Please answer them on these pages provided. Partial credit will be awarded.
11. A sign is suspended from the side of a building
by a steel wire and steel pole as shown. The sign
has a mass of 150 kg, and the mass of the pole,
fittings and wire are negligible.
a. Draw a free body diagram for the steel pole in
this situation.
b. What is the weight of the sign?
c. What is the vertical component (only) of the
tension in the wire?
d. What is total wire tension T?
e. What are the size and direction of the normal
force applied to the pipe by the wall?
50 
90 
40 
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PHY111 Exam 2
10/25/00
M1 (23 kg) and M2 (15 kg) are connected by
a pulley and string on an inclined plane with
= 25˚ as shown. µ = 0.15
(a) Draw a free body diagram for this situation.
Indicate your coordinate axes.
(b) Write Newton's Second Law for x and y
motions of this situation.
MacIsaac
Page
12.
M1
M2

(c) Write an expression for the acceleration of this system, and solve it (find a).
(d) Write an expression for the string tension, and solve it (find T).
PHY111 Exam 2
10/25/00
MacIsaac
Page
13.
The motion of objects orbiting a planet (orbital mechanics) can be described and predicted by
combining the relationships between uniform circular velocity, gravitational attraction and centripetal
acceleration.
a. Use these three relationships to derive two formulas, one for orbital velocity in terms of planetary mass
and orbital radius, and the other describing the relationship between orbital period, radius and planetary
mass. Show your work.
Mars has two tiny moons named Phobos (foe-bus) and Deimos (dee-mos). Phobos has an orbital period of
7.7 hours and orbits at average radius 9,410 km. Deimos has an average orbital radius of 23,500 km.
b. What is the orbital period of Deimos?
c. What is the mass of Mars?
The International Space Station (ISS) is currently being constructed in low Earth orbit at an altitude of
285 km. The Earth's average radius is 6,370 km.
d. What is the orbital velocity of ISS?
e. What is the orbital period of the ISS?