Download Practice Midterm

Physics 100
Midterm
Name:______________
Date: March 6, 2002
This is a closed book exam. Useful formulas and constants are located on the back page.
I. Multiple Choice (2 pts each)
1. Venus is usually either the “evening star” or the “morning star” because
(a) it is usually on the same side of the sun, relative to Earth.
(b) its orbit around the sun is inside Earth’s orbit
(c) its orbit around the sun is outside Earth’s orbit
(d) it is usually on the opposite side of the sun, relative to Earth.
(e) actually, the evening or morning star is usually Mars, not Venus
2. Which of the following scientists first developed the theory that planets circle the sun
rather than circling the Earth?
(a) Ptolemy
(b) Copernicus
(c) Kepler
(d) Galileo
(e) Brahe
3. Which of these is the correct definition of an ellipse?
(a) Each point on the ellipse lies on a smooth oval curve around one fixed point.
(b) Each point on the ellipse is the same distance from one fixed point.
(c) Each pair of points on the ellipse is the same distance from one fixed point.
(d) All points on the ellipse are an equal distance apart.
(e) The sum of the two distances of a point on the ellipse from two fixed points is the
same, for each point on the ellipse.
4. Tycho Brahe’s extremely precise measurements of the planetary positions showed that
(a) Copernicus’ theory was wrong and Ptolemy’s theory was correct.
(b) Ptolemy’s theory was wrong and Copernicus’ theory was correct.
(c) both Ptolemy’s and Copernicus’ theories were wrong.
(d) both Ptolemy’s and Copernicus’ theories were correct.
(e) Kepler’s theories were wrong.
5. Is it possible to prove, for certain, that a scientific theory is true?
(a) No, because of the experimental error, or uncertainty, that is present in any
experimental result.
(b) No, because it is always possible that a future experiment will disagree with the
theory
(c) Yes, by means of a single confirmed experiment that verifies a theory.
(d) Yes, by deducing it logically from other scientific theories that are known to be true.
(e) Yes, by carrying out a sufficient number of experimental observations
6. Today, the idea that everything is made of atoms should be classified as
(a) a fact
(b) a certainty
(c) both of the above
(d) a theory
(e) a hypothesis
7. The number of atoms in the glucose molecule H2SO4 is
(a) 7
(b) 6
(c) 4
(d) 3
(e) cannot be determined from the given information
8. In powers of ten expression, 35 million is
(a) 3.5*107
(b) 3.5*108
(c) 3.5*109
(d) 3.5*1010
(e) 3.5*1011
HINT: write this number out before trying to answer the question
9. At the microscopic level, the difference between gases and liquids is that
(a) the gas’s atoms move throughout the gas, while the liquid’s atoms remain near their
original locations
(b) there is much more distance (at least 10 times more) between neighboring atoms in a
gas than between neighboring atoms in a liquid
(c) in a gas, the individual atoms are larger
(d) both answers “a” and “b” are correct
(e) both answers “b” and “c” are correct
10. Which item in the list is the lightest in weight?
(a) water molecule
(b) oxygen atom
(c) hydrogen atom
(d) electron
(e) proton
11. According to Galileo, a ball that rolls along a surface and comes to rest stops because
(a) its natural motion is to come to rest
(b) of its inertia
(c) of gravity
(d) of friction
(e) the ether slows it down to a stop
12. What keeps the moon moving, i.e., why doesn’t the moon slow down and stop?
(a) Earth’s gravity keeps it moving
(b) the sun’s gravity keeps it moving
(c) It is actually slowing down, and will come to rest in a few thousand more years
(d) Nuclear processes operating in the central core of the moon
(e) It is the natural motion of every object to keep moving by itself.
13. While a rock is falling down it has
(a) an unchanging velocity
(b) an increasing velocity
(c) zero velocity
(d) a decreasing velocity
(e) none of the above
14. Suppose we subject a golf ball and a more massive lead ball to the same net forces.
Then, compared to the golf ball, the lead ball must have
(a) a smaller speed
(b) a larger speed
(c) a smaller acceleration
(d) a larger acceleration
(e) no one of the above answers is necessarily true
15. A ball is rolling on the floor towards the west, and slowing down as it rolls. As it is
rolling,
(a) the net force on it is to the east
(b) its velocity is towards the east
(c) both of the above
(d) the net force on it is zero
(e) the net force on it is toward the west
II. Problems (10 pts each) - Show your work! Please include units in your answer.
1. Is 1 mile closest to 2000 meters, 2000 feet, or 20,000 inches? First, show how many
meters, feet, and inches are equivalent to 1 mile.
2. Your UR parking space is so far away that you decide to bike 6 km to Krispy Kreme.
You manage to get there in 12 minutes and 30 seconds.
(a) What is your average speed (in m/s)?
(b) If you start off from rest and increase to a speed of 6 m/s in the first two and a half
minutes of your journey, what is your average acceleration during those 150 seconds (in
m/(s^2))?
(c) How far will you have traveled in that time (m)?
(d) If it takes you 10 minutes to travel the remaining distance, what is your average speed
for the rest of the trip (in m/s)?
3. Suppose you throw your 2 kg physics book out a fifth-floor window of Rush Rhees
(note: this is not recommended).
(a) What is the force due to gravity on the book (approximate the acceleration due to
gravity to the nearest whole number)?
(b) Suppose that air resistance causes a 2 Newton force in the direction opposite the
book’s motion as it falls. What is the book’s acceleration?
(c) With air resistance, how much time does it take for the book to hit the ground,
(d) With air resistance, what is the book’s velocity when it hits the ground 18 meters
below?
Short Answer Questions -- 10 pts each
1. If you were looking at the North Star at the North Pole, in which direction would the
surrounding stars appear to turn? Why?
2. What is the chemical formula for carbon dioxide (one carbon atom and one oxygen
atoms)? Sulfur dioxide (the abbreviation for sulfur is “S”)? Sulfur trioxide? Water?
3. Two bicyclers pass one another on the same road, traveling in opposite directions.
Could they possibly have the same velocity? The same speed? Explain.
4. (a) Would it be easier to lift your TA on Earth or on the moon?
(b) Neglecting friction, would it be easier to set your TA into horizontal motion on Earth
or on the moon?
(c) Neglecting friction, would it be easier to set your TA into horizontal motion on Earth
or in distant space?
Useful Formulas and Constants
In the following formulas,
F = force (Newtons)
m = mass (kilograms)
a = acceleration (meters/(second^2))
t = time (seconds)
d = distance (meters)
v = velocity
F  ma
d
1 2
at ,
2
when the object starts at rest
t
2d
,
a
when the object starts at rest
v  at ,
when the object starts at rest
The acceleration due to gravity on Earth is 9.8 m/(s^2). You may approximate 10
m/(s^2) for this exam.
acceleration = (change in velocity)/(change in time)
velocity = (change in position)/(change in time)
Conversion table
1 inch = 2.54 centimeters (you may approximate 1 inch = 2.5 centimeters on this exam)
12 inches = 1 foot
5280 feet = 1 mile
100 centimeters = 1 meter
1000 meters = 1 kilometer
1 minute = 60 seconds
1 hour = 60 minutes