Quest Chapter 13. Where is the event happening? What does the no atmosphere phrase mean in the problem? What is the ball doing during the event?

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1 1 (part 1 of 2) A ball is tossed straight up from the surface of a small, spherical asteroid with no atmosphere. The ball rises to a height equal to the asteroid s radius and then falls straight down toward the surface of the asteroid. What forces, if any, act on the ball while it is on the way up? 1. Both a constant gravitational force that acts downward and a decreasing force that acts upward 2. No forces act on the ball. 3. Only a decreasing gravitational force that acts downward 4. Only an increasing gravitational force that acts downward 5. Only a constant gravitational force that acts downward 2 (part 2 of 2) 10.0 points The acceleration of the ball at the top of its path is 1. zero. 2. equal to the acceleration at the surface of the asteroid. 3. at its maximum value for the ball s flight. 4. equal to one-half the acceleration at the surface of the asteroid. 5. equal to one-fourth the acceleration at the surface of the asteroid. 3 Which of the objects a. a book b. the nearest star c. the Sun d. a distant galaxy exert(s) a gravitational force on you? Quest Chapter 13 Where is the event happening? What does the no atmosphere phrase mean in the problem? What is the ball doing during the event? What is changing as it does this? This is a projectile motion problem. Review your notes from chapter 3. What causes gravitational force? Which items in the list have this characteristic?

2 4 Two iron spheres of mass m and 2m, respectively, and equally spaced points r apart are shown in the figure. At which location would the net gravitational force on an object due to these two spheres be a maximum? 1. A 2. B 3. C 4. E 5. D 5 (part 1 of 3) a 58.7 kg person would experience while standing on the surface of Earth with a mass of kg and a radius of m. The universal gravitational constant is (part 2 of 3) on Mars, with a mass of kg and a radius of m. 7 (part 3 of 3) on Pluto, with a mass of kg and a radius of m. 8 The gravitational force of attraction between two students sitting at their desks in physics class is N. If one student has a mass of 58.1 kg and the other has a mass of 63 kg, how far apart are the students sitting? The universal gravitational constant is What are the factors you must consider in this problem? Masses and distances. What happens to the net force on the object if it is between the two masses? Will the net force be greater outside on the left or outside on the right? Same person. Same person.

3 9 Planet X has nine times the diameter and two times the mass of the earth. What is the ratio g X : g e of gravitational acceleration at the surface of planet X to the gravitational acceleration at the surface of the Earth? Nine times the diameter is what change in the radius? Remember: As the diameter changes, so does the radius. 10 Two planets with the same diameter are close to each other, as shown. One planet has twice the mass as the other planet. At which locations would both planets gravitational force pull on you in the same direction? From among these four locations, where would you stand so that the force of gravity on you is a maximum; i.e., at which point would you weigh the most? 1. D; D 2. C; A 3. A and B; D 4. B and C; C 5. B and C; D 6. A and D; A 7. A and D; D 8. None of these 9. B; D 11 The Earth and the moon are attracted to each other by gravitational force. The more massive Earth attracts the less massive moon with a force that is (greater than, less than, the same as) the force with which the moon attracts the Earth. 1. the same as 2. less than 3. greater than 4. Unable to determine Find the multiple of Earth s a g. For the first part of the problem, the direction, what position(s) would the force vectors toward the two planets be pointed in the same direction? Select the answers that agree with your analysis. For the second part, maximum force, consider the hint to problem 4. Look at the gravitation equation. Is the force on mass 1 calculated differently from the force on mass 2?

4 12 The environment in a satellite or space station orbiting the Earth is often referred to as weightless environment; however, we have defined weight as the force of gravity on an object. In this sense, what statement is not correct concerning an object on board an orbiting satellite? 1. The object is weightless. 2. The weight of an object in orbit is only a few percent less than it is on the Earth. 3. We refer to the object in orbit as weightless because it is accelerating toward the Earth, but it is not actually weightless. 4. There is a force of gravity on the object. 13 If the earth were of uniform density, what would be the value of g inside the earth at half its radius? (The value of g at the surface of earth is 9.8 m/s 2.) m/s m/s m/s m/s 2 What statement is NOT correct? Read for understanding. Eliminate correct statements. What is g inside a hollow sphere? (zero) How would you describe the Earth is the inner half (radius r/2) were removed? What would be g inside that new Earth? 14 The gravitation force of the Moon obeys Newton s law of general gravitation and is responsible for tides on the oceans of Earth. Select the diagram which best describes the effect of the tides on the oceans on Earth. The diagrams show an exaggerated amount of water on the surface of the Earth (shown in gray) and make the assumption that the whole Earth is covered with water. Assume also that the only relevant force causing the tides is the gravitational force. What would g be if the rest was return and you were at r/2 radius? What does the gravitation effect of the moon do to the liquid water on the planet? How would you see that if you were observing from far out in space?

5 15 How can we observe a black hole if neither matter nor radiation can escape from it? 1. We can observe the gravitational effect of the black hole on a visible star s orbit located near it. 2. We can use X-ray telescopes which are very sensitive to very short wavelengths. 3. We can observe the radiation from it. 4. We can detect its emitted gravitational radiation. 16 The planet Krypton has a mass of kg and radius of m. What is the acceleration of an object in free fall near the surface of Krypton? The gravitational constant is Earth s gravitational field is 8.46 N/kg at the altitude of the space shuttle. What is the size of the force of attraction between a student of mass 57.8 kg and Earth? Answer in units of N 18 The mass of a certain neutron star is kg (6 solar masses) and its radius is 2200 m. What is the acceleration of gravity at the surface of this condensed, burned-out star? The value of the universal gravitational constant is (part 1 of 2) The asteroid Ceres has a mass kg and a radius of km. What is g on the surface? The value of the universal gravitational constant is (part 2 of 2) How much would an 87.7 kg astronaut weigh on this asteroid? Answer in units of N What escapes from a black hole? What would a black hole cause other objects to do? You know that: F g = Gm 1 m 2 /r 2 for an object m 1 and Krypton m 2 at a distance r. Remember: a g = Gm 2 /r 2 N/kg? What are the units you get when you solve the second law of motion for a? F = ma (N = kg * a) So, the 8.46 N/kg is just an acceleration due to gravity. Use the second law. See the note for 16. See the note for 16. Use the second law of motion and your answer from 19.