EXAM I, PHYSICS 1408-001, October 3, 2007
Dr. Charles W. Myles
INSTRUCTIONS: Please read ALL of these before doing anything else!!!
1. PLEASE put your name on every sheet of paper you use and write on one side of the paper
only!! PLEASE DO NOT write on the exam sheets, there will not be room!
2. PLEASE show all work, writing the essential steps in the problem solution. Write
appropriate formulas first, then put in numbers. Partial credit will be LIBERAL, provided
that essential work is shown. Organized, logical, easy to follow work will receive more credit
than disorganized work.
3. The setup (PHYSICS) of a problem will count more heavily than the math of working it out.
4. PLEASE write neatly. Before handing in your solutions, PLEASE: a) number the pages and
put the pages in numerical order, b) put the problem solutions in numerical order, and c)
clearly mark your final answers. If I can’t read or find your answer, you can't expect me to
give it the credit it deserves.
NOTE!!! I HAVE 65 EXAMS TO GRADE!!! PLEASE
HELP ME GRADE THEM EFFICIENTLY BY
FOLLOWING THE ABOVE SIMPLE INSTRUCTIONS!!!
FAILURE TO FOLLOW THEM MAY RESULT IN A
LOWER GRADE!! THANKS!!
A 3’’ x 5’’ card with anything on it & a calculator are allowed. Problem 1
(Conceptual Questions) IS REQUIRED! Answer any two (2) of the remaining
problems for a total of three (3) problems required. Problem 1 is worth 34 points.
Problems 2, 3, 4 & 5 are equally weighted & worth 33 points each.
1. REQUIRED CONCEPTUAL QUESTIONS!!! Answer these briefly. Most
answers should be a few complete, grammatically correct English sentences. Keep
formulas to a minimum. Use WORDS instead! If you use a formula, DEFINE ALL
symbols you use.
a. State Newton’s 1st Law. How many objects at a time does it apply to? State
Newton’s 3rd Law. How many objects at a time does it apply to?
b. State the Work-Kinetic Energy Theorem.
c. See figure. A hockey puck is sliding (to the right) at
constant velocity across a flat, horizontal, frictionless ice
surface. Which of the sketches is the correct free body
diagram? WHY? (Normal force in figure is called FN instead of n, as
our text does). Explain your answer using Newton’s Laws!
(Hint: Is there a force in the motion direction?) To answer correctly, you must think like
Newton (of more than 300 years ago) NOT like Aristotle (of more than 3,000 years ago)!
d. See figure. A rider of mass m is on a Ferris wheel moving in a

vertical circle of radius r at constant speed v. The free body
n2  ac 
diagrams for the rider at the top & bottom of the ride are
mg 
shown. (Normal force in figure is called FN instead of n, as our text

does). Expanded views of the free body diagrams are at the
Bottom
right of the Ferris wheel. Is the normal force n1 that the seat
exerts on the rider at the top, more than, equal to, or less than the normal force n2
at the bottom? WHY? Explain your answer (with WORDS, as well as equations) using
Newton’s 2nd Law with centripetal acceleration.

n1  ac 
mg 

Top
NOTE: Answer any two (2) of problems 2, 3, 4, & 5!!!
2. See figure. A cannon ball is shot from the ground with an initial velocity vi = 50 m/s
at an angle θi = 50° with the horizontal. It lands on
top of a building of height h = 45 m above the
ground. Neglect air resistance. To answer this, take
vi
xi = yi = 0 where the cannon ball is shot. It’s
θi
probably best to take the upward direction as
positive! (Hint: That the building height is 45 m
above the ground is totally irrelevant to every question
but that in part f!)
----------------- d

|
h
|

------------------
a. Calculate the horizontal & vertical components of the initial velocity vi.
b. Calculate the cannon ball’s maximum height above the ground. Calculate the
time it takes to reach that maximum height.
c. Calculate cannon ball’s horizontal (x) distance from the starting point when it has
reached it’s maximum height.
d. Calculate the horizontal & vertical components of velocity, vx & vy, after the
cannon ball has been in the air for 4.8 s. Calculate the ball’s velocity (magnitude and
direction) after it has been in the air for this same time.
e. 5 POINT BONUS! Calculate the time it takes the cannon ball to land on top of
the building. When it does so, calculate it’s horizontal distance d from its starting
point. (Hint: You will need to use the quadratic equation to answer this!).
3. See figure. A clerk pushes a carton on a dolly with a force F =
65 N making an angle θ = 33° below the horizontal. The mass
(carton + dolly) is m = 14 kg. A friction force Ff between the dolly
& the floor acts in the opposite direction of the motion. The
θ
F
kinetic friction coefficient between the box & the floor is μk =
Ff
0.16. Use the x & y axes shown.
a. Sketch the free body diagram of the carton + dolly, properly
labeling all forces. Don’t forget the weight & the normal force n, not shown in
the figure! Calculate the x & y components of the pushing force F.
b. Calculate the weight of the carton plus dolly & the normal force n the floor exerts
on them. Is n equal (& oppositely directed) to the weight? Why or why not? Justify
your answer with Newton’s 2nd Law in the direction perpendicular to the floor.
Calculate the friction force Ff that the dolly experiences as it moves to the right.
c. Use Newton’s 2nd Law to find the acceleration a experienced by the carton plus
dolly. What forces cause this acceleration?
The clerk pushes the carton + dolly a horizontal displacement Δx = 40 m across the room.
d. Calculate the work done by the pushing force F in this process. Calculate the
work done by friction force Ff in this process. Calculate the net work done by all
forces in this process.
e. If the carton + dolly starts from rest, calculate their kinetic energy and speed after
the clerk has pushed them through a displacement Δx = 45 m.
a 
NOTE: Answer any two (2) of problems 2, 3, 4, & 5!!!
4. See figure. A car, mass m = 1625 kg, drives at constant speed v =
18 m/s on a straight road. It passes over a bump of circular cross
section. The bump radius of curvature is r = 33 m. Neglect the
driver’s mass.
a. Calculate the car’s centripetal acceleration & the “centripetal
force” on it when it is at the top of the bump. What is their
r = 35 m
direction?
b. Sketch the car’s free body diagram, properly labeling all forces. Don’t forget the
normal force n on the car due to the road when it’s at the top of the bump. Is there
a force in the motion direction (along the road)? WHY or WHY NOT?
c. Write the equation resulting from applying Newton’s 2nd Law in the vertical
direction to the car at the top of the bump. Writing it in general, without numbers
will get more credit than writing it with numbers in!
d. Use the equation from part c to find the normal force n on the car at the top of the
bump. Is n equal to & opposite to the car’s weight? WHY or WHY NOT?
5. The figure is the free body diagram for a
crate, mass m = 50 kg, which is pulled a
distance x = 40 m across a flat, horizontal
floor. It is being pulled by a constant force
FP = 100 N, making an angle θ = 37° with
the horizontal as shown. There is NO
vertical motion. There is a friction force Ffr
= 50 N between the crate & the floor. The
normal force between the crate & the floor is called FN in the figure, rather than n, as
your text does.
a. Calculate the work done by the pulling force FP in this process.
b. Calculate the work done by the friction force Ffr in this process.
c. Calculate the work done by the normal force FN and the work done by the weight
mg in this process.
d. Calculate the net work done by all forces in this process. If the crate starts from
rest, calculate it’s kinetic energy and speed after it has gone x = 40 m.