Practice Exam 4
•
You may use one regular (3” x 5”) index card for your formulas or any other notes or diagrams you think you may need (front & back).
Definitions & Concepts
1.
The state of an object or system in which all external forces are in balance. a.
Stress b.
Dynamics c.
Equilibrium d.
Strain
2.
What is the magnitude of the phase angle difference between the position and the velocity of an object undergoing simple harmonic motion? a.
0 o b.
90 o c.
180
(
π
/2) o
(
π
)
3.
What is the shortest distance between a satellite’s orbit and the Earth called? a.
Ellipse b.
Semi-major axis c.
Eccentricity d.
Perigee
4.
True or False: This is one of Kepler’s
Laws: “The planets orbit the sun in circles, with the sun at the center of the circle.” a.
True b.
False
Applications
5.
How much closer (in km) is Mars to the sun when at perihelion than at aphelion?
6.
What is the escape velocity from the surface of the planet Mars, whose mass is 6.46x10
23
kg and whose radius is 2.109x10
6
m? What is the surface gravitational acceleration on Mars?
7.
A rock is transported to a spot 2 Earth radii above the surface of the Earth and released from rest. Ignoring atmospheric drag, how fast is the rock traveling right before it impacts the surface?
8.
A lead sphere is formed with a diameter of 1 m and a mass of 5760 kg. What is the magnitude of the gravity field due to this sphere at a point 2 meters from its surface? If a small lead sphere of diameter 0.01 m and mass 0.00576 kg is placed 2 meters from the surface of the large sphere, what is the magnitude of the gravitational force of the large sphere on the small one?
9.
A length of wire of unknown metal with diameter 0.4 mm and originally 2.000 meters long is observed to stretch to 0.01 mm when a weight of 100 N is hung from its end. What is the value of Young’s modulus of the unknown metal?
R. Gist 1 of 2 Long Semester Ver. B, Rev. 1

Practice Exam 4
10.
What is the tension in cable AC in the diagram to the right?
11.
A 3 meter uniform beam ( AD ) weighing
300 N is supported by a strut at B and a cord at D . A box weighing 20 N is placed at C . If distance AB is 0.6 meters and distance BC is 1.6 meters, what is the tension in the cord? What is the compression in the strut?
12.
A simple harmonic oscillator is built from a 10 kg block on wheels attached to a wall using a horizontal spring (with spring constant k=9000 N/m). At time t =0, the block is struck to start it oscillating, such that its initial speed as it leaves equilibrium ( x =0) is 10 m/s. Find the following: (a) The angular frequency of the oscillation; (b) The period of oscillation of the block; (c) The maximum displacement of the block; (d) The maximum acceleration of the block; (e) The total energy contained in the system; (f) The distance from equilibrium of the block at t =0.5 seconds.
13.
Andrew sits on planet X and measures the distance from it to its moon to be 100,000 km. Bob, who is traveling at half the speed of light, measures the same distance as he sees the planet and moon go by him. What distance does Bob measure? How long a time interval does Bob measure to travel from the moon to planet X? How long a time interval does Andrew observe for Bob to travel from moon to planet X?
Constants:
Universal Gravitational Constant
Radius of Mars
Mass of Mars
Mars
Mean distance between Mars and the sun
Eccentricity of Mars orbit
Mean distance between Earth and the sun
G=6.67 x 10
-11 d=2.28x10
8 e=0.093
N*m
2
R
Mars
=2.109x10
6
m
M
Mars
=6.46x10
23
kg
km d
S
=1.497 x 10
11
/kg
2
m (1 AU)
R. Gist 2 of 2 Long Semester Ver. B, Rev. 1