Ch3 Laws of Motion Test Questions & Answers - Understanding Our Universe 3e Complete Test Bank by Stacy Palen. DOCX document preview.
Chapter 3: Laws of Motion
LEARNING OBJECTIVES
3.1 Astronomers Have Studied the Motions of the Planets Since Ancient Times
3.1a Distinguish between geocentric and heliocentric models of the Solar System.
3.1b Describe Kepler’s laws.
3.2 Galileo Was the First Modern Scientist
3.2a Explain how Galileo applied the scientific method to refute the geocentric model and promote a heliocentric worldview.
3.3 Newton’s Laws Govern Motion
3.3a Relate inertia and mass.
3.3b Describe Newton’s first law of motion when applied to objects moving in different physical situations.
3.3c Describe the difference between speed, velocity, and acceleration.
3.3d Apply Newton’s second law of motion to determine if objects will accelerate under a different set of physical situations.
3.3e Apply Newton’s third law by considering action-reaction pairs in different physical situations.
3.4 Gravity Is a Force between Any Two Massive Objects
3.4a Differentiate gravity, mass, and weight.
3.4b Apply Newton’s universal law of gravitation to quantify the attractive force between objects.
3.4c Understand the inverse square law.
3.5 Orbits Are One Body “Falling Around” Another
3.5a Describe the difference between empirical and physical laws.
3.5b Explain why planetary objects in orbit are in a perpetual state of free fall.
3.5c Relate an object’s speed to its orbital position.
Working It Out 3.1
Working It Out 3.1a Use Kepler’s third law to determine the orbital period of planetary objects or their orbital semimajor axis.
Working It Out 3.2
Working It Out 3.2a Use Newton’s second law to calculate acceleration.
Working It Out 3.3
Working It Out 3.3a Evaluate physical laws through proportionalities.
Chapter 3: Laws of Motion
MULTIPLE CHOICE
1. Which scientist ended up under house arrest because of his support of the heliocentric model?
a. Galileo Galilei c. Johannes Kepler
b. Isaac Newton d. Tycho Brahe
2. Which of the following is true about a comet that is on an elliptical orbit around the Sun?
a. The comet’s speed is greatest when it is farthest from the Sun.
b. The comet’s speed is greatest when it is nearest the Sun.
c. This comet’s speed is zero.
d. The comet’s speed is constant because its mass and the Sun’s mass stay approximately the same.
3. Which of the following pair of orbital parameters appear in Kepler’s third law?
a. eccentricity and the semimajor axis c. the period and the semimajor axis
b. eccentricity and the period d. the period and the semiminor axis
4. Which orbital feature controls the shape of a planet's orbit?
a. eccentricity c. orbital period
b. semimajor axis d. orbital speed
5. Which of the following ellipses has the largest eccentricity?
a. c.
b. d.
6. What do the Copernican and Ptolemaic models have in common?
a. elliptical orbits c. circular orbits
b. Sun as center of the universe d. Earth as center of universe
7. Which of the following could be observed without the use of a telescope?
a. spots on the Sun c. phases of Venus
b. retrograde motion of the planets d. Jupiter’s moons
8. Pluto has an orbital period of 248 years. Using Kepler’s third law, what is the semimajor axis of Pluto?
a. 6.3 AU c. 39.5 AU
b. 15.7 AU d. 61,504 AU
9. Which observations made by Galileo are inconsistent with the geocentric model of astronomy?
a. craters on the Moon
b. orbits of Jupiter’s moons and phases of Venus
c. retrograde motion of Mars
d. sunspots
10. Newton’s first law states that objects in motion
a. eventually come to rest.
b. experience an unbalanced force.
c. experience a nonzero acceleration.
d. stay in motion unless acted upon by an external force.
11. If an object is moving in a circular orbit at a constant speed, which of the following is true?
a. It accelerates. c. Its velocity is constant.
b. Its acceleration is zero. d. There is no force acting on it.
12. How are mass and inertia related?
a. More massive objects contain more inertia.
b. Less massive objects contain more inertia.
c. Inertia and mass are unrelated.
d. Only masses in motion contain inertia.
13. In which of the following situations would the object be experiencing an unbalanced force?
a. truck at rest
b. car moving at constant speed turning a corner
c. rocket moving at a constant speed straight up away from Earth
d. car moving at a constant speed and direction due east
14. The natural tendency of an object to resist changes in motion is called
a. inertia. c. acceleration.
b. weight. d. mass.
15. The sloshing of coffee in a cup as a car slows down, speeds up, or turns is due to
a. the force of gravity.
b. the coffee’s weight.
c. inertia.
d. the contact forces between the molecules of the material.
16. As the astronaut depicted here pushes a wrench away from himself, which arrow best describes the force acting on him?
a. c.
b. d.
17. As the astronaut depicted here pushes a wrench away from himself, which arrow best describes the acceleration acting on him?
a. c.
b. d.
18. What do the arrows depicted here represent after an astronaut pushes a wrench away from himself?
a. forces acting on each c. velocities of each
b. accelerations acting on each d. masses of each
19. What is your acceleration if you go from 30 to 60 miles per hour (mph) in 4 seconds?
a. 60 mph/s c. 15 mph/s
b. 30 mph/s d. 7.5 mph/s
20. In a spaceship orbiting Earth, two astronauts want to measure the mass of a mouse. How can they easily do it if they are in constant free fall?
a. Place the mouse on a spring-loaded scale and weigh it.
b. Measure the gravitational attraction between the mouse and a steel ball of known mass.
c. Drop the mouse from the top of the spaceship to its bottom.
d. Push on the mouse with a known force and measure its acceleration.
21. If a 100-kg astronaut pushes on a 5,000-kg satellite and the satellite experiences an acceleration of 0.2 m/s2, what is the acceleration experienced by the astronaut in the opposite direction?
a. 5 m/s2 c. 50 m/s2
b. 10 m/s2 d. 0.1 m/s2
22. In the following figure, if the woman pushes with a force of 200 newtons (N), what will be the acceleration of the container? Assume negligible friction between the cart and floor.
a. 0.5 m/s2 c. 1 m/s2
b. 0.75 m/s2 d. 2 m/s2
23. You apply a force of 10 N to a grocery cart to get an acceleration of 0.5 m/s2. If you apply a force of 20 N to the same grocery cart, its acceleration will be
a. 10 m/s2. c. 0.5 m/s2.
b. 1 m/s2. d. 0.25 m/s2.
24. In the following figure, if the acceleration of the container is 0.5 m/s2, with what force did the woman push? Assume negligible friction between the cart and floor.
a. 50 N c. 150 N
b. 100 N d. 200 N
25. What force holds planets in their orbits?
a. air resistance c. electromagnetic
b. friction d. gravity
26. The force of gravity exerted on an object is directly related to its
a. inertia. c. mass.
b. size. d. density.
27. Which of the following properties of an astronaut changes when he or she is standing on the Moon, relative to when the astronaut is standing on Earth?
a. weight c. inertia
b. mass d. all choices are correct
28. Your weight is directly proportional to your
a. height. c. mass.
b. age. d. altitude.
29. In the absence of air friction, a 0.001-kg piece of paper and a 0.1-kg notebook are dropped and allowed to fall to the ground. How do their accelerations compare? The
a. accelerations are the same.
b. notebook’s acceleration is 100 times faster than the paper’s acceleration.
c. notebook’s acceleration is 1,000 times faster than the paper’s acceleration.
d. paper’s acceleration is 100 times faster than the notebook’s acceleration.
30. Two rocks (call them S and T) are a distance of 50 km from one another. Rock S has 20 times the mass of rock T. Which rock will move faster if the only force involved is their mutual gravitational attraction?
a. rock S
b. Both rocks will move at the same speed.
c. rock T
d. Not enough information is available to answer.
31. If your weight on the Moon is 1/6 your weight on Earth, what is the weight of a 100 kg mass on the Moon?
a. 9.8 N c. 100 N
b. 980 N d. 163 N
32. If your weight on the Moon is 1/6 your weight on Earth, what is the acceleration caused by gravity on the Moon?
a. 9.8 m/s2 c. 0.17 m/s2
b. 58.8 m/s2 d. 1.60 m/s2
33. Tripling the radius of a sphere causes what change in the surface area?
a. three times more c. nine times more
b. six times more d. no change
34. If your weight on Earth was 500 N, what would your weight be on the Moon?
a. 83 N c. 250 N
b. 125 N d. 500 N
35. According to the inverse square law, what is the impact on the force of gravity between two masses if their separation is doubled? The
a. force doubles. c. force is halved.
b. force quadruples. d. force is quartered.
36. If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would
a. decrease by a factor of 4. c. increase by a factor of 2.
b. decrease by a factor of 2. d. increase by a factor of 4.
37. If the distance between Earth and the Sun were doubled, the gravitational force between these two objects would
a. decrease by a factor of 4. c. increase by a factor of 2.
b. decrease by a factor of 2. d. increase by a factor of 4.
38. Suppose you are suddenly transported to a planet with one-fourth the mass of Earth but the same radius as Earth. Your weight would __________ by a factor of __________.
a. increase; 4 c. decrease; 4
b. increase; 16 d. decrease; 16
39. Suppose you are suddenly transported to a planet with one-fourth the radius of Earth but the same mass as Earth. Your weight would __________ by a factor of __________.
a. increase; 4 c. decrease; 4
b. increase; 16 d. decrease; 16
40. Suppose you are suddenly transported to a planet with twice the radius of Earth and eight times the mass of Earth. Your weight would __________ by a factor of __________.
a. increase; 2 c. decrease; 2
b. increase; 8 d. decrease; 8
41. How much would the force of gravity at the surface of the Earth differ if Earth’s volume were increased 125 times and its mass was increased 25 times? (Hint: Volume is proportional to the cube of a sphere’s radius.)
a. 25 times less c. 25 times larger
b. no difference d. 125 times less
42. If you weighed 150 pounds on Earth, what would you weigh on Mars? For reference, Mars has a mass that is 0.1 times Earth’s mass, and Mars has a radius that is 0.5 times Earth’s radius.
a. 30 pounds c. 76 pounds
b. 110 pounds d. 60 pounds
43. The force of gravity between Earth and the Sun is approximately __________ the force of gravity between Earth and the Moon. For reference, the average distance between Earth and the Moon is 0.003 astronomical units (AU), the mass of the Moon is 7 
1022 kg, and the mass of the Sun is 2 1030 kg.
a. 86,000 times larger than c. 140 times smaller than
b. 260 times larger than d. 6,400 times smaller than
44. How much would the force of Earth’s gravity at its surface differ if the Earth’s volume were increased 1,000 times and its mass was increased 250 times? (Hint: Volume is proportional to the cube of a sphere’s radius.)
a. 2.5 times less c. no difference
b. 2.5 times larger d. 0.25 times less
45. What type of orbit results when a satellite has a velocity greater than the escape velocity?
a. unbound c. circular
b. bound d. linear
46. Once a satellite’s velocity at closest approach equals or exceeds the __________ velocity, it is in an unbound orbit.
a. tangential c. circular
b. linear d. escape
47. What is true about a circular orbit?
a. Speed must be constant.
b. Speed varies.
c. It’s the fastest speed of all possible orbits.
d. It exceeds the escape velocity.
48. What is true about an elliptical orbit?
a. Speed must be constant. c. It is unbound.
b. Speed varies. d. It exceeds the escape velocity.
49. What is true for both circular and elliptical orbits?
a. Speeds are constant. c. They are bound.
b. Speeds vary. d. Their eccentricities are nonzero.
50. Astronauts orbiting Earth in a spacecraft feel weightless in space because
a. they are farther away from Earth.
b. they have reached escape velocity.
c. the added gravitational pull of the Moon balances Earth’s gravitational pull.
d. they are in constant free fall around Earth.
51. What must an object be doing to be considered in orbit around the Earth?
a. constantly propelled
b. escaping gravity
c. constantly moving away from Earth
d. in a state of constant free fall around the Earth
52. What will happen to an object whose tangential velocity at closest approach about the Earth is less than the circular velocity?
a. It falls to Earth. c. The orbit becomes elliptical.
b. It maintains a circular orbit. d. It escapes.
53. An empirical science is one that is based on
a. assumptions. c. computer models.
b. calculus. d. observed data.
1. In a period of time t, a planet travels a distance of 30,000 km with an average speed of 10.5 km/s. Some time later, the same planet travels 65,000 km in the same time t. How fast is the planet traveling at this later time? During which period is the planet closer to the Sun?
2. List at least three discoveries Galileo made by making astronomical observations through a telescope.
3. What is required to change an object’s uniform motion?
4. According to Newton’s third law, forces come in pairs. Two forces in the following figure are labeled. Label the other half of the pairs.
5. Name the two ways in which an object’s motion (meaning its velocity) can experience a nonzero acceleration.
6. Given a constant acceleration from rest, how is the increase in speed computed?
7. In the following figure, draw an arrow representing the direction of the acceleration in each case. If the acceleration is zero, write zero.
8. If every action of a force is met by an equal but opposite force, why does anything accelerate?
9. An analogy of orbital motion is the twirling of a ball connected by a string. What is the action-reaction force pair described by Newton’s third law?
10. Examine the following figure. If the woman pushes with a force of 100 N, what is the acceleration of the container? Ignore friction.
11. What acceleration would result from a 5-N force acting on a 3-kg object? (A newton has units of kg•m/s2.)
12. Examine the following figure. If the acceleration of the container is 0.5 m/s2, with what force did the woman push?
13. If a 100-kg asteroid collides with Earth, causing the asteroid to decelerate in 1 second from 1,000 m/s to 0 m/s, what acceleration will Earth experience according to Newton’s third law? (Earth has a mass of approximately 6 1024 kg.)
14. Astronauts feel “weightless” on the Moon. Using Newton’s universal law of gravitation, explain why astronauts experience this feeling.
15. Explain what the inverse square law for gravity means and give an example.
16. Is there a difference in your weight between when you are on top of a mountain at 1,000 meters above sea level compared with when you are sitting in a classroom at 10 meters above sea level?
17. How much stronger is the gravitational force of the Sun on Earth compared with the gravitational force of the Sun on Mars? Note that Mars’s semimajor axis is 1.5 AU, and its mass is 0.1 times the mass of Earth.
18. Explain the difference between being weightless and being in free fall.
19. The following figure shows Newton’s cannonball thought experiment. At the three locations of the cannonball shown, draw and label arrows representing the circular velocity and acceleration. Ignore air resistance.
20. An object in a circular orbit is in a perpetual state of free fall—that is, accelerating toward Earth but never reaching it. Explain.