exam

Physics 100
Exam 1

For the acceleration due to gravity, let g = 10 m/s/s for calculations.

Useful equations:
v = d/t
a = (vf - vi)/t
d = vi t + 0.5 at2
vf = vi + at
d = 0.5(vi + vf) t
F = m a
F = G m1 m2 / d2
g = G m / d2
a3 = T2
c = 3 x 108 m

1. Which could be a unit for acceleration?
a. m/s
b. m/s/s
c. mile/hr/s
d. m/s2
e. all but a

2. Consider an object in freefall with no air resistance. How fast will it be traveling (approximately) after 2.5 seconds of falling?
a. 2.5 m/s
b. 25 m/s
c. 30 m/s
d. 27.5 m/s
e. there is not enough information

3. You are seated at a baseball game and you notice that the ball leaves the bat BEFORE you hear the crack of the bat. Why is this?
a. the speed of sound is greater than the speed of light
b. the speed of light is greater than the speed of sound
c. the speed of light equals the speed of sound in air
d. your view of the game is blocked by some jerk with big hair
e. this actually can NOT possibly happen - you must be mistaken, or perhaps there is an echo

4. Seasons on Earth are the result of:
a. the tilt of the the Earth's axis
b. Earth getting closer and further from the Sun
c. Kepler's 3rd law
d. the variable output of the Sun's radiation
e. the Earth's magnetosphere

5. Consider dropping a heavy object on the Moon from rest. How does the time to fall compare with the same object dropped from the same height on Earth? Assume no air resistance.
a. it is less
b. it is the same
c. it is more
d. the answer depends on the mass of the object

6. The SI unit of mass is the ____ and it is currently based on _____.
a. gram, chunk of metal
b. gram, water
c. kilogram, water
d. kilogram, speed of light
e. kilogram, chunk of metal

7. The SI unit of length is the _____ and it is currently based on _____.
a. meter, distance from North pole to equator
b. meter, two lines on a platinum-iridium bar
c. kilometer, speed of light
d. meter, speed of light
e. mile, speed of light

8. Consider the following situation: a ball is dropped from rest. At the SAME time, another identical ball is shot horizontally from the same height. Which ball lands first? There is no air resistance.
a. the horizontally shot ball
b. the dropped ball
c. they land at the same time
d. there is not enough information to tell

9. What is the celestial sphere?

a. the path of the Earth around the Sun
b. a model of the universe with the Earth at the center
c. a model of the universe with the Sun at the center
d. the Sun
e. an epicycle

10. Consider a person standing on a large steel cart with low-friction wheels. This person is holding a pole - this pole suspends a giant magnet a constant distance from the front of the cart. Assuming that this magnet normally attracts steel, will this make the cart move?



a. yes - Newton's third law demands it
b. no - the action and reaction forces cancel each other on the cart
c. yes, but only if the magnet weighs more than the cart and person
d. no - because the magnet does not affect the rubber tires
e. yes, but only enough to barely make the cart move at a constant speed


11-12. Consider the planet Jupiter traveling around the Sun.

11. If Jupiter is 5 AU from the Sun, how long (in years) does it take to orbit the Sun once?
a. 5
b. 10
c. 53
d. 25
e. square root of 53

12. What is the shape of Jupiter's orbit?
a. figure 8
b. circle
c. hyperbola
d. ellipse
e. parabola

13. What is an Astronomical Unit?
a. the amount of time required for Earth to orbit once
b. the amount of time required for Earth to rotate once
c. the size of Earth's semi-major axis (in orbit around the Sun)
d. the average distance to the Moon
e. the diameter of the Solar System

14. What is an epicycle?
a. the elliptical path that every planet takes
b. the circular path that every planet takes
c. the apparent path of the Sun through the sky
d. a concept used to explain retrograde motion
e. a device used to measure the distance to a star

15. Consider an extremely sensitive electronic scale that measures weight. You have a tightly sealed jar of live flies on the scale. Will the scale reading change, based on the flies' position?
a. yes - it will read the most when the flies are moving around
b. no - it will not change at all, regardless of the flies' motion
c. yes - it will read the most when the flies are resting on the bottom of the jar
d. yes - it will read the most when the flies are attached to the sides of the jar
e. yes - it will read the most if the flies are on the top of inside of the lid (upside-down)

16. During what month is the Earth nearest the Sun?
a. June
b. September
c. March
d. January
e. It's actually different every year

17. Which statement is true about the Earth's speed as it moves around the Sun?
a. it is fastest when nearest the Sun
b. it is unchanging, more or less
c. it is fastest when farthest from the Sun

18. Consider a see-saw, initially at rest. A 20 kg child sits 1.5-m from the fulcrum on the left. Where should a 30 kg child sit so that the see-saw is balanced?

a. 3-m from the fulcrum on the right
b. 2-m from the fulcrum on the right
c. 1-m from the fulcrum on the right
d. the 30 kg child can not balance the 20 kg child
e. 2.5-m from the fulcrum on the right

19. Imagine balancing a broom horizontally on your finger. Which end is heaviest?
a. A
b. B
c. both ends weigh the same

20-21. Consider standing on a scale that measures your weight. You and the scale are in an elevator.

20. If the elevator were accelerating upward, what would be true of your weight reading?
a. it would be less than normal
b. it would be zero
c. it would be greater than normal

21. If the cable snapped (yikes!), what would the scale read?
a. your normal weight
b. greater than your normal weight
c. less than your normal weight, but not zero
d. zero
e. 9.8 m/s/s

22. Newton's major work was _____ and was published in _____.
a. Principia Mathematica, 1787
b. Principa Mathematica, 1687
c. De Revolutionibus, 1543
d. De Revolutionibus, 1687
e. Almagest, 1687

23. Imagine if you had a baseball somehow equipped with a speedometer. If the ball were dropped, how would the reading on the speedometer change (if at all)?
a. it would reach 9.8 m/s and stay there
b. it would increase by 9.8 m/s every second
c. it would decrease by 9.8 m/s every second
d. it would increase by an amount less than 9.8 m/s every second
e. it would increase by an amount greater than 9.8 m/s every second

24. Which is the longest day of the year?

a. autumnal equinox
b. vernal equinox
c. summer solstice
d. winter solstice
e. none of these

25. If you were standing on the Moon, which statement would be true?
a. your mass and weight would be less than on Earth
b. your mass would be less than your Earth mass, but your weight would remain unchanged
c. your weight would be less than your Earth weight, but your mass would remain unchanged
d. your mass would be greater than your Earth mass, but your weight would remain unchanged
e. your mass and weight would both remain unchanged

26. What is the approximate value for g at a distance above sea level equal to one Earth radius?
a. 10 m/s/s
b. 5 m/s/s
c. 1 m/s/s
d. 0 m/s/s
e. 2.5 m/s/s

27. How far (in m) would a light pulse travel in 10 seconds?
a. (3 x 108) x 10
b. 3 x 108
c. (3 x 108) x 100
d. (3 x 108) x 1000
e. (3 x 108) x 0.1

28. The Moon is approximately how far from us?
a. one light-second
b. one light-year
c. one light-day
d. one light-month
e. one light-nanosecond

29. How long have we known/believed that the Earth was spherical?
a. since the time of Columbus
b. since the Scientific Revolution and Galileo
c. since the ancient Greeks lived
d. since we were able to see it from space
e. since the 1800s

30. Consider 2 massive bodies in space. The distance between is changed to 4 times the original distance. What happens to the gravitational force between the bodies?
a. it is 16 times greater
b. it is 1/16 as much
c. it remains the same
d. it is quadrupled
e. it is ¼ as much

31. A car is accelerating at a rate of 2 m/s/s. If it starts from rest, how fast will it be traveling after 7 seconds?
a. 7 m/s
b. 9 m/s
c. 2/7 m/s
d. 7/2 m/s
e. 14 m/s

32. In the above problem, how far will the car travel during this time?
a. 14 m
b. 49 m
c. 7 m
d. 98 m
e. 25 m

33. To measure the size of the Earth, Eratosthenes:

a. walked from the equator to the North Pole
b. used sticks and shadows
c. compared the Earth to the Moon
d. compared the Earth to Mars
e. watched a lunar eclipse

34. What is the weight of a 65 kg woman?
a. 65 kg
b. 65 N
c. 650 kg
d. 650 N
e. 650 lb

35. If you were to push on a 10-kg box with a force of 50-N, what would happen? Assume no friction.
a. it would accelerate
b. it would move at a constant speed of 5 m/s
c. it would move at a constant speed of 0.2 m/s
d. it would not move
e. it is impossible to say

36. Imagine a spring scale - it has a hook at the top for hanging up, and a spring-loaded hook at the bottom for weighing things. Now this spring scale is placed horizontally with two equal 10-N weights attached to each side by strings. The weights are draped over frictionless pulleys as shown. What does the scale read?

a. 20-N
b. 0-N
c. 5-N
d. 10-N
e. some other value

37. Consider throwing a ball straight up in the air. At the top of its path:

a. the speed is 9.8 m/s
b. the speed is the same as it was in your hand
c. the acceleration is 9.8 m/s/s upward
d. the acceleration is 0
e. the speed is 0
38. Consider a horizontal curved piece of hose. Water is sent out of the tube. Which path does the water take?


a. A
b. B
c. C

39. Recall the balancing guy demonstration. Where is the center of mass likely to be located? See diagram.

a. A
b. B
c. C
d. D
e. E

40. Traveling to Philadelphia, you could either drive at a constant 65 mph or an average 65 mph. In general, which method will get you to Philadelphia sooner?

a. Constant speed
b. Average speed
c. They are the same time for both
d. Why would you want to go to Philadelphia?

41. The speed of light is so fast that a pulse could travel:
a. around the Earth's equator once in a second
b. around the Earth's equator 1000 times in one second
c. from New York to Los Angeles in 1 second
d. from the North Pole to the South Pole in 1 second
e. around the Earth's equator 7 times in 1 second

42. A bowling ball and a golf ball are dropped simultaneously from the same height. There is no air resistance. Which lands first?
a. bowling ball
b. golf ball
c. same time for each

43. Consider an airplane flight. You toss a bag of airline snacks straight up as the plane cruises along at 500 miles/hr. Where do the snacks land?
a. behind you
b. in front of you
c. to the left OR right of you
d. in your hands
e. it is impossible to say

44. This is a graph of distance versus time for a car. What is the car doing in this interval?

a. Nothing - it is stopped
b. Accelerating
c. Moving with constant speed
d. Slowing down
e. speeding up, then slowing down

45. Which historical ordering of scientists is correct:

a. Copernicus, Newton, Galileo
b. Newton, Galileo, Copernicus
c. Copernicus, Galileo, Newton
d. Galileo, Copernicus, Newton
e. Newton, Copernicus, Galileo

Bonus. On March 31, 2012, what awesome thing is happening in DC?