Note: These problems are designed to require more thinking than traditional problems. Some problems may require techniques from more than one chapter. Some problems may have more than one reasonable solution. Some problems may have no solution, in which case it is your job to explain why there is no solution, the data you would need to obtain a solution, and how you would use this data to obtain a solution. Some problems may include irrelevant information. Some problems may include nonSI units, but your solutions must be given in SI. Some problems may require reasonable assumptions such as freefall, minimal friction, etc. All solutions must show work to receive full credit. All solutions should be presented symbolically before plugging in numbers. All solutions must include acknowledgements. All problems using Newton's laws must include free body diagrams to receive full credit. Each force must have a type, direction, approximate magnitude, source, and receiver clearly identified.
Imagine that you are a dictator who would like to impose a new system of units on your nation as an exercise in your arbitrary power. Invent and describe this system of units.
Include the following in your description:

base units
(skip current and luminous intensity)

some
derived
units

a
discussion of the merits of this system (precision, universality,
stability, simplicity, etc.)
You should be creative, comprehensive, and critical. You should not worry about being practical. You are not required to have the same base dimensions (distance, time, etc.) as SI. For example, you could have a base acceleration and distance and then derive the time unit.
A flower pot falls from a balcony of an apartment building in Salem, Oregon and injures a person. Your job is to determine the apartment from which it originated. Video footage from the second floor indicates that it traveled past a 4.000 meter high window in 0.2600 seconds. All floors in the building are 4.000 meters high. From which floor was the flower pot dropped? Hint:
don't even think about using v = d/t
or any variation thereof (6th grade kinematics) at any
point in this problem.
The shot put is a track and field event involving "putting" (throwing in a pushing motion) a heavy metal ball (called the shot) as far as possible. A shot putter starts from rest, accelerates the shot uniformly in a straight line, and releases the shot at 15 m/s. How far did his hand move?
The shot put is a track and field event involving "putting" (throwing in a pushing motion) a heavy metal ball (called the shot) as far as possible. A shot putter starts from rest, accelerates the shot uniformly in a straight line at 60 m/s^{2 }for 0.20 seconds, and releases the shot at 15 m/s. How far did his hand move?
A care package is delivered by an airplane by dropping
it out the bottom. The airplane is flying horizontally
at a speed of 75 m/s. The airplane is 120 meters above
horizontal ground. Assume that air resistance is
negligible for the care package from the time of release
to the time it hits the ground.

Determine the acceleration (x and y components) of
the care package just after it is dropped.

Determine the acceleration (x and y components) of
the care package just before it hits the ground.

Determine the time it takes the package to hit the
ground.

Determine the velocity (x and y components) of the
care package just before it hits the ground.

Determine the velocity (magnitude and direction) of
the care package just before it hits the ground.
A rare "snow day" in Salem, Oregon gives you the opportunity to go sledding. As you drag your sled across level ground at constant speed, you wonder what the coefficient of friction of the snow on the sled is. You estimate the following:

You pull on the rope with a 1.2 pound force

The sled weighs 10 pounds

The sled moves with a speed of 1.5 m/s

The rope makes an angle of 25 degrees to the level ground
You are passing a construction site near building 8 on the Chemeketa campus. You see the construction workers leave for a break, but they have left a large concrete block resting at the top of a wooden ramp. As soon as their backs are turned, the block begins to slide down the ramp. Estimate the length of the ramp based on the following information:

It takes 9 seconds for the block to reach the bottom of the ramp

The ramp appears to be straight and at an angle of about 20 degrees above horizontal

Your physics book states that the coefficient of kinetic friction between concrete and wood is 0.35
Your friend plans to drive her 1100kg car at a constant 40 mph over the top of a hill that is shaped in a circular arc (radius = 60 feet). Predict the magnitudes of each of the forces on the car at the top. You may assume drag and friction are negligible. You may ignore the mass of your friend.
It has been proposed that an athletic club use the energy from its customers (on stationary bikes, treadmills, etc.) to generate some of its electricity. You have been hired by the athletic club to calculate the monthly value of harvesting this energy based on the following:

The average customer burns 8.6 Calories per minute

The average customer is 25% efficient at converting food energy into electrical energy

There are 20 customers using exercise machines on average throughout the day

The athletic club is open 18 hours per day

Electricity is worth $0.15 per kWh
Some train stations have large horizontal springs at the ends of the tracks. These are safety devices to stop the train so that it will not go plowing through the station in the event an engineer is too busy texting. You would like to know how fast a train could be going and still be safely stopped by the spring. You would also like to know the spring constant of the spring. It looks like the spring can be compressed about 3.0 meters. The maximum safe acceleration for passengers while stopping is about half of g. You know from years of reading books about trains that a typical train has a mass of 5.0E5 kg.
While getting hit in the head with a falling coconut is not a significant cause of death, it is reasonable to assume that it is an unpleasant experience. In order to estimate the damage from a coconut, it is desirable to know the
average force of impact (among other things). Use the following data to calculate an
average force of impact for a coconut on a person's head:

The coconut tree is at the equator near sea level

The
coconut has a mass of 1.7 kg

The coconut falls from a height of 20 m

The coconut hits a person of height 2 m and mass of 80 kg

The coconut is in contact with the person's head for 0.040 seconds

The coconut has a negligible velocity after the collision
You are a Navy officer ordered to design an effective airplane launcher. The launcher consists of a large spring that pushes the plane for the first 6 meters of a 22 meter long runway. The plane's engines can supply a constant thrust of 5.4E4 N for the entire length of the runway. In order for the two (metric) ton plane to successfully take off, it must have a speed of at least 44 m/s by the end of the runway.

What is the minimum spring constant for the launcher?

Using this spring, what will be the maximum acceleration of the plane (and its pilot)?

Based on this maximum acceleration, do you think this is a good design? Why or why not? If not, what would you suggest changing (thrust, mass, spring, runway, etc.)? Assume you cannot change the needed speed.
You have a friend who is entering a skateboarding competition in Los Angeles. She wants to take a running start and then jump onto her 5 kg stationary skateboard. She will then roll along a 2 meter section of level track and go up a sloped concrete ramp. She wants to reach a maximum height of at least 3 meters above where she started. She can run with a maximum speed of 8 m/s and has a mass of 50 kg. Will this trick work?
As a good physicist and a helicopter parent, you would like to check if your children's cartoons present correct physics. In one cartoon, Tarzan is in peril from a stampede of wildebeests. Lucky for him, Jane is nearby. She grabs a vine and swings down to a stationary Tarzan to save him. At the bottom of the swing, she grabs him. They both continue to swing to safety up to a height which looks to be about onethird that of Jane's original height. It appears that Tarzan has twice the mass of Jane. Decide if you are going to let your children watch this cartoon based on whether or not it is correct physics.
You are in charge of designing a racetrack. It has already been determined that the track will be circular and have a diameter of 1 mile. The owners would like cars to be able to drive in a circle at 110 mph without depending on friction.

Calculate the angle of the banking of the track.

If a car drives at 170 mph, calculate the minimum static coefficient of friction necessary to do so. You may ignore all forces from the air.
A ball is attached to a string (extentionless and massless, of course) of length L. The string is attached to a frictionless pivot point. When the string is vertical, the ball is a distance h above the horizontal ground. The ball and string are released from rest at an angle Θ_{1}
from the y axis (Θ_{1} < 90°) and the string is straight. You may place a sharp knife somewhere so that it cuts the string and allows the ball to launch from a chosen angle, Θ_{2}. Derive a symbolic expression (in terms of the given variables and possibly other constants such as g) for the following:

Launch speed

Landing speed

Height attained after launch as measured from the ground

Height attained after launch as measured from the launch point

Time of flight

Horizontal distance as measured from a fixed location on the ground which is directly below the ball and string when they hang vertically

Horizontal distance as measured from the launch point
Now set L = 2.00 m, h = 0.50 m, and Θ_{1} = 40°. Calculate the maximum possible value and the Θ_{2} necessary to do so for each of the above quantities. You should end up with 7 symbolic solutions, 7 calculations of maximum, and 7 calculations of Θ_{2}.
Yes, this is a very tough problem. This means that there is an opportunity for extra credit if you do excellent work.
Your friend is going to court to determine fault in an automobile accident in Paris, Texas. She thinks that the other car was speeding and she was not. She is looking to you for help to prove her assertion. During discovery, the following evidence is presented, none of which is disputed by the other driver:

Weather records indicate that there was no rain the day of the collision

Your friend was traveling north just before the collision and the other car was traveling east

The two cars got stuck together and remained so after the collision while skidding to a stop

The speed limit on both roads is 45 mph

The accident occurred on level ground

Measurements of skid marks created after the collision indicate that the cars skidded 50 feet at an angle of 30 degrees north of east before stopping

According to driver's manuals, your friend's car weighs 2400 lbs and the other car weighs 2000 lbs. Each driver weighs 150 lbs and there was no significant cargo

A physics textbook indicates that the coefficient of kinetic friction for rubber on dry pavement is 0.80
What can an analysis of the physics of this collision and aftermath tell the court regarding the speeds of each of the vehicles before they collided?
Joey Joey took a stone
And knocked
Down
The
Sun!
And whoosh! it swizzled
Down so hard,
And bloomp! it bounced
In his backyard,
And glunk! it landed
On his toe!
And the world was dark,
And the corn wouldn't grow,
And the wind wouldn't blow,
And the cock wouldn't crow,
And it always was
Night,
Night,
Night.
All because
Of a stone
And Joe.
Shel Silverstein
How fast did Joey have to throw a stone to hit the sun? Ignore air resistance. The stone need not make the sun land in his backyard.
A rod of length L and mass m is attached to a pivot at one end. The rod is rotated to an angle of nearly 90 degrees above horizontal and released from rest. It is observed to rotate to horizontal. At the instant of release:

find the moment of inertia of the rod rotating about the fixed end

find the magnitude of the torque on the rod

find the magnitude of the angular velocity of the rod

find the magnitude of the angular acceleration of the rod

find the magnitude of the velocity of the tip of the rod

find the magnitude of the tangential acceleration of the tip of the rod

find the magnitude of the centripetal acceleration of the tip of the rod

find the vertical acceleration of the tip of the rod

find the horizontal acceleration of the tip of the rod

find the vertical acceleration of the center of the rod

find the horizontal acceleration of the of the center of the rod

find the x and y components of the force exerted by the pivot point
At the instant just before the rod hits the ground:

find the moment of inertia of the rod rotating about the fixed end

find the magnitude of the torque on the rod

find the magnitude of the angular velocity of the rod (hint: use conservation of energy)

find the magnitude of the angular acceleration of the rod

find the magnitude of the velocity of the tip of the rod

find the magnitude of the tangential acceleration of the tip of the rod

find the magnitude of the centripetal acceleration of the tip of the rod

find the vertical acceleration of the tip of the rod

find the horizontal acceleration of the tip of the rod

find the vertical acceleration of the center of the rod

find the horizontal acceleration of the of the center of the rod

find the x and y components of the force exerted by the pivot point

compare the above value to g and thoroughly explain any difference
At some angle θ above horizontal:

find the moment of inertia of the rod rotating about the fixed end

find the magnitude of the torque on the rod

find the magnitude of the angular velocity of the rod (hint: use conservation of energy)

find the magnitude of the angular acceleration of the rod

find the magnitude of the velocity of the tip of the rod

find the magnitude of the tangential acceleration of the tip of the rod

find the magnitude of the centripetal acceleration of the tip of the rod

find the vertical acceleration of the tip of the rod

find the horizontal acceleration of the tip of the rod

find the vertical acceleration of the center of the rod

find the horizontal acceleration of the center of the rod

find the x and y components of the force exerted by the pivot point
All solutions must be in terms of g, L, m, and
Θ¸. Show your work, but place the results of your solution in a table like the following:
Quantity

Any Θ

Θ = 90° (vertical)

Θ = 0° (horizontal)

I




τ




ω




α




v




a_{tan }(tip)




a_{cp }(tip)




a_{y} (tip)




a_{x} (tip) 



a_{y} (center) 



a_{x} (center) 



F_{y} 



F_{x} 



Answer these followup questions:

At what angle above horizontal will the magnitude of the vertical acceleration of the tip of the rod be equal to g?

At what angle above horizontal will the magnitude of the vertical acceleration of the tip be a maximum? What is the maximum acceleration? How can it be greater than g?
A rod of length L and mass m is attached to a pivot at one end. The rod is attached to a point mass (mass M) at some location on the rod. The rod is rotated to an angle of θ degrees above horizontal and released from rest.
Design a pendulum with a period of 5.00 s that will function inside a 1 m^{3} cube. It must work in an inertial reference frame on Earth. Do not use any springs,
magnets, or charged objects.
Hint: a simple, smallangle pendulum will not work.
How deep would a typical balloon need to pulled down
into the ocean so that it would sink instead of float?
You may make the following assumptions:
 The pressure inside the balloon is the same as
its surroundings.
 The radius of the balloon when inflated (to
roughly a sphere) in the
atmosphere is 25
cm.
 The density of air inside the balloon before it
is put in the ocean is 1.3 kg/m^3.
 The temperature of the air inside the balloon
does not change.
 The balloon material is 6 micrometers thick and
has an unchanging density of 1390 kg/m^3
 The air inside the balloon obeys the ideal gas
law.
Hints: determine the following in order (don't worry
about waiting until the end to plug in numbers):
 total mass using geometry and the definition of
density
 total volume displaced at equilibrium using
Newton's second law
 volume of the air alone at equilibrium
 pressure in the air at equilibrium using the
ideal gas law
 depth at equilibrium using the formula for
pressure at depth in a static fluid
You are given a stopwatch and a simple pendulum of length 2.00000 m. The pendulum can undergo 100 oscillations before they become too small to notice. You know that your stopwatch
uncertainty is about 0.10 s. How high must you climb in order to detect a significant difference in the period of the pendulum?
Suppose you drill a hole through the center of the Earth all the way to the other side and then drop a rock.
 Calculate the speed of the rock at the center of the Earth.
 Calculate the time it would take a rock to go all the way through.
Hints: Assume that the Earth has uniform density and that the hole doesn't have any air. Only the matter in the sphere closer to the center than the rock exerts a net gravitational force on the rock. Ignore the rotation of the Earth.
A cube of iron of height Y is released just below the surface of a large vat of mercury. The top face of the cube is parallel to the surface of the mercury.
Determine the time it takes the cube to return to the point of release
in terms of the dimensions of the cube and empirical
constants. Assume that the drag force of the mercury and the buoyant force of the air are negligible.
A small, solid ball is near the bottom of a hemispheric bowl of
radius 13 cm. It rolls without sliding to the other side
of the bowl. Determine the time it takes to do so.
You've been hired as a consultant to the police department to design a new device that measures the speed of vehicles. The idea is to make a small, rugged device to be placed in the road that will pick out a specific frequency emitted by the car as it approaches and then measure the frequency as it recedes. The device will then use this data to calculate the speed of the car. You are currently in the process of writing a program for the chip in your new device. To complete the program, you need a formula that determines the speed of the car using the measured frequencies. You may also include in your formula any physical constants that you might need.
 Derive this formula. Note that the source frequency is not known.
 What could you do (other than improve the quality or quantity of frequency data gathered) to improve the accuracy of this device?
Many exercise machines at gyms will provide you with
data on both your power output (usually in watts) and
your metabolic power (usually in Calories/minute; note
the big "C"). The ratio of power output to metabolic
power (be sure to use the same units) is the
manufacturers implicit assumption of the efficiency of
the human body. For you or for someone you know:
 Determine this efficiency
 Assume that energy output is worth $0.15 per kWh
(3.6 million joules). If you were to hook up a
person to a generator, determine how much money an
hour's worth of exercise is worth.
Hints: Be sure to distinguish between energy and
power. Power is energy/time. And be careful with units
as many are not SI.
Define temperature. The definition should not be an ordinal definition based on direction of heat flow or a measure of "hotness" or "coldness". It should be something that can be calculated based on other measurable quantities (at least in principle). Do not use the ideal gas law (or variations thereof) as it is only approximate.
Define entropy. Do not simply say it is a measure of disorder which is not a precise mathematical statement. It should be something that can be calculated based on other measurable quantities (at least in principle).
The MaxwellBoltzmann speed probability distribution is the following:
f(v) = âˆš[(2/Ï€)(m/(kT))^3]v^2*e^[mv^2/(2kT)]
m = mass
k = Boltzmannâ€™s constant = 1.381E23 J/K
v = speed
T = temperature
Calculate the average speed (v_{ave}) and most probable speed (v_{p}). Hints:
Bonus: Find the rootmeansquare speed (v_{rms}) in terms of m, k, and T.
Bonus: Find the fraction of protons predicted by the MaxwellBoltzmann distribution to have a speed greater than the speed of light (integrate from c to infinity), given a very large temperature, say 7.3E10 K. Find a temperature for which the MaxwellBoltzmann distribution predicts a significant fraction of the particles (you decide the threshold) will have a speed above that of light.
Two small spheres are suspended by strings of length L = 1.20 m from a ceiling at points d = 3.20 m apart. They have equal mass of m = 8.00 kg and equal and opposite charge of q = 1.40E4 C. Calculate the angle or angles the strings make from vertical at equilibrium.
It has been proposed that lightning be harvested for energy. Measurements of lightning strikes indicate that they have the following average properties (note, these are reasonable approximations):
 Potential difference between each end of 100 million V
 Current of 30000 A
 Time of 1.67E4 seconds
 20 strikes per square kilometer per year in lightning prone regions of the United States and 200 strikes per square kilometer per year in the most lightning prone regions in the world (Congo).
"Lightning collectors" have the following properties
(I'm just making these up, though I think they are wildly optimistic):
 They can only collect lightning that would strike within a 100 m x 100 m area
 They each cost $10,000
 They last 40 years
 Maintenance costs and scrap value are negligible
The following economic data are also known (these are very rough estimations):
 Electrical energy is worth about $0.12 per kWh and is not expected to increase in value
 Investors in such projects expect to get back triple their initial investment in total after 40 years
As an independent energy consultant, it is your job to check if this project is a good investment in either the United States or Congo. Provide a report detailing your assertions and your reasoning. Assume that your audience is investors who have perhaps taken high school physics or college physics many years ago. You will be graded on both the correctness of your physics (and accounting) and your ability to explain the physics to such an audience.
Given that the angular momentum of the lowest energy orbit of an electron in orbit in a hydrogen atom is the reduced Planck constant,
h_bar = 1.056E34 J*s, calculate the radius of its (assumed circular) orbit. Solve symbolically in terms of
h_bar and other known constants (mass, etc.). Plug in your numbers to obtain the radius.
Given a 9 V battery with internal resistance of 0.80 ohms hooked to a single resistor of variable resistance, calculate and graph the current, potential difference, and power for the variable resistor over the range 0 to 5 ohms. What is the resistance of maximum power? Prove your assertion based on your graph and calculus.
Given the following graph of potential as a function of x, graph the electric field as a function of x. Provide an exact recipe (dimensions of objects, amount of charge, locations) in order to create such electric potentials and fields.
A long wire on the xaxis carries 25 A of current to the right. A rectangular loop (0.70 m wide and 0.80 m height) of 36 gauge copper wire in the xy plane begins with its center at a location of 0.45 meters directly above the wire. The loop moves in the positive x direction at a constant speed of 0.20 m/s for 5.0 seconds. It then moves in the positive y direction at a constant speed of 0.20 m/s for 5.0 seconds.

Calculate and graph the magnetic flux through the loop as a function of vertical position of the center of the loop. The area vector should be assumed to be on a positive axis.

Calculate and graph the magnetic flux through the loop as a function of time.

Calculate and graph the induced emf in the loop as a function of time.

Calculate and graph the induced current in the loop as a function of time. Use the convention that clockwise currents are negative and counterclockwise currents are positive.

Calculate and graph the electric power of the loop as a function of time.

Calculate and graph the force on the loop as a function of time.
Hint: the magnetic field is not constant over the entire area of the loop. If you treat the magnetic field as fixed over the entire area, you will certainly lose a great deal of credit on this problem.
Given figure P35.50 with the values as shown, (a) Calculate the resonant frequency in rad/s. (b) Calculate Z, I, V_{R}, V_{c}, V_{L}, V_{RL}, and V_{LC} at this frequency. (c) Redo part b for double and half the resonant frequency.
