EXAM I, PHYSICS 1403-003 (MWF)
February 18, 2005
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: IN THE 2 SECTIONS, I HAVE 260 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!! THANK YOU!!
A 8.5’’ x 11’’ sheet 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, and 4 are equally weighted & worth 33 points each.
1. THIS PROBLEM IS REQUIRED!!! CONCEPTUAL QUESTIONS: Answer
these briefly, in a few complete and grammatically correct English sentences.
a. State Newton’s 1st Law and Newton’s 3rd Law.
b. See figure. You are riding in a convertible with the top down. The car is
moving to the right (x-direction) at constant velocity v0x. You throw a ball
straight up (from your viewpoint) with an initial velocity v0y while the car
travels forward at v0x. Neglect air resistance. Will the ball land behind
the car, in front of the car, or in the car? WHY? Explain (briefly!) your
answer. Use what you know about projectiles!. Make a sketch of the situation to
illustrate your explanation.
c. See figure. A box is sliding at constant velocity (v = constant!) across a
v
flat, horizontal, frictionless surface. Sketch the free body diagram for
this box. Is there a force in the direction of the box’s motion? Explain
your answer using Newton’s Laws!
d. Answer the following for a 5 POINT BONUS! During our class
discussion about projectiles, I did an in-class demonstration which tried to
illustrate the answer to question b, about the person in the convertible. Briefly
describe this demonstration. (If you were in class when I did this demonstration,
you should be able to answer this. If you “cut” class that day, as many of you
often do, you probably won’t be able to answer it!)
NOTE:
Answer any two (2) of problems 2, 3, & 4!!!
2. See figure. A cannon ball is shot from the
ground with an initial velocity v0 = 48 m/s at
h
an angle θ0 = 60° with the horizontal. It lands
θ
on top of a nearby building of height h = 42
m above the ground. Neglect air resistance.
To answer these questions, take x = y = 0
--------------------------- d -----------------------
where the cannon ball is shot. It is probably
best to take the upward direction as positive! (Hint: That the building’s height is 42 m
above the ground is totally irrelevant to every question but that in part e!)
a. Compute the horizontal & vertical components of the initial velocity.
b. Compute the cannon ball’s maximum height above the ground. Compute the time
it takes to reach this height.
c. Compute it’s horizontal (x) distance from the starting point when it has reached
it’s maximum height.
d. Compute the horizontal & vertical components of velocity, vx & vy, after the
cannon ball has been in the air for 5 s. Compute the stone’s velocity (magnitude or
length and direction) after it has been in the air for this same time.
e. 5 POINT BONUS! Compute the time it takes the cannon ball to land on the top
of the building. When it does so, compute 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 stock clerk pushes on a carton on a dolly. He pushes
with a force F = 65 N which makes an angle θ = 37° below the
horizontal. The mass of the carton + dolly is m = 10 kg. There
is a frictional force Ff between the dolly & the floor, acting in
the opposite direction of the motion. The coefficient of kinetic
friction between the box & the floor is μk = 0.15. To solve this
problem, use the x & y axes shown.
Ff
θ
F
a. Draw the free body diagram of the carton + dolly, properly labeling all
a 
forces. Don’t forget the weight & the normal force, not shown in the figure!
Compute the x & y components of the pushing force F.
b. Compute the weight of the carton plus dolly & the normal force FN the floor
exerts on them. Is this normal force equal (& oppositely directed) to the weight? If so,
why? If not, why not? Justify your answer using Newton’s 2nd Law in the
direction perpendicular to the floor.
c. Compute the frictional force Ff that the dolly experiences as it moves to the right.
d. Use Newton’s 2nd Law to find the acceleration a experienced by the carton plus
dolly. What forces cause this acceleration?
NOTE: Answer any two (2) of problems 2, 3, & 4!!!
4. See figure. Two masses, m1 = 20 kg & m2 = 30 kg, are connected by a massless cord
over a massless, frictionless pulley. m1 sits on a flat,
horizontal frictionless table & m2 hangs vertically. An
m1, a = 8.0 m/s2 

unknown force FP pulls downward on m2. This causes m1 to
FT
2
accelerate to the right with acceleration a = 8.0 m/s & m2 to
accelerate downward with the same acceleration.
a. Draw the free body diagrams for the two masses, properly

labeling all forces. For m1, be sure to include the tension
FP
FT in the cord & to include both horizontal & vertical

forces.

b. The two unknowns are the pulling force FP & the tension, FT, in the
cord. By applying Newton’s 2nd Law to m1 & m2, find the two equations
needed to solve for FP & FT. Writing these equations in symbols, without
substituting in numbers, will receive more credit than writing them with numbers
substituted in!
c. Using the equations from part b, compute (find numerical values for) the two
unknown forces FP & FT.
d. If mass m1 starts from rest, compute it’s velocity & the distance it has traveled
after t = 1.0 s.
FT
m2
a = 8.0 m/s2

