Physics Chapters 8 & 9
In what sense does the Moon "fall"? The Moon "falls" away from Earth a bit on every orbit. The Moon does not "fall." Instead, it moves in a circle at a constant radius. The Moon "falls" toward Earth a bit on every orbit. It falls away from the straight path that it would follow if there were no forces acting on it.
It falls away from the straight path that it would follow if there were no forces acting on it.
Find the change in the gravitational force between two planets if the masses of both planets are doubled but the distance between them stays the same. Express your answer as an integer.
F(new)/F = 4
Calculate the force of gravity on the 1-kg mass if it were 1.3×107 m above Earth's surface (that is, if it were three Earth radii from Earth's center).
F= 1.1 N
F= G (m1m2)/(d^2) Calculate the force of gravity between Earth (mass = 6.0×1024kg) and the Moon (mass = 7.4×1022 kg ). The average Earth-Moon distance is 3.8×108 m . Express your answer to two significant figures and include the appropriate units.
F= 2.1x 10^20 N
Centripetal Force: F=(mv^2)/r Calculate the tension in a horizontal string that whirls a 2.3-kg toy in a circle of radius 2.3 m when it moves at 2.9 m/s on any icy surface
F= 8.4 N
Why does the gravity in the Space Shuttle compare with the gravity on Earth the way it does? The Space Shuttle is much farther away from the center of the Earth than the surface of the Earth. The Space Shuttle is much closer to the center of the Earth than the surface of the Earth. The Space Shuttle is about the same distance from the center of the Earth than from the surface of the Earth.
The Space Shuttle is about the same distance from the center of the Earth than from the surface of the Earth.
Your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight? The elevator moves upward with constant velocity. The elevator moves downward with constant velocity. The elevator moves upward while slowing in speed. The elevator moves downward while slowing in speed. The elevator moves downward while increasing in speed.
The elevator moves downward while slowing in speed.
If you are standing on a scale in an elevator, what exactly does the scale measure? your mass the force you exert on the scale the gravitational force exerted on you by Earth
the force you exert on the scale.
If you stood on a planet having a mass four times that of Earth, and a radius two times that of Earth, how much would you weigh on that planet? two times your weight on Earth one-half your weight on Earth the same as your weight on Earth one-fourth your weight on Earth four times your weight on Earth
the same as your weight on Earth.
Using the universal law of gravity, we can find the weight of an object feeling the gravitational pull of a nearby planet. We can write an expression w=GmM/r2, where w is the weight of the object, G is the gravitational constant, m is the mass of that object, M is mass of the planet, and r is the distance from the center of the planet to the object. If the object is on the surface of the planet, r is simply the radius of the planet. The gravitational field on the surface of the earth is stronger than that on the surface of the moon. If a rock is transported from the moon to the earth, which properties of the rock change? mass only weight only both mass and weight neither mass nor weight
weight only
If one person is pushing to the right on a 300-kg cart with a force of 200 N, and another person is pushing to the left on the same cart with a force of 100 N, what is the acceleration of the cart? 0.33 m/s/s 1 m/s/s 3 m/s/s 100 m/s/s
0.33 m/s/s
Which of the following quantities represent mass? Check all that apply. 12.0 lbs 0.34 g 120 kg 1600 kN 0.34 m 411 cm 899 MN
0.34 g 120 kg
Which of the following quantities would be acceptable representations of weight? Check all that apply. 12.0 lbs 0.34 g 120 kg 1600 kN 0.34 m 411 cm 899 MN
12.0 lbs 1600 kN 899 MN
What happens to the strength of the gravitational field at the surface of a star that shrinks? It stays the same. It decreases. It first increases and then it decreases. It increases.
It increases.
State Newton's law of universal gravitation in words. Then do the same with one equation. The force is proportional to the product of two masses and inversely proportional to the distance between their centers: F ~ m1m2/d. The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ m1m2/d2. The force is proportional to the product of two masses and to the square of the distance between their centers: F ~ m1m2d2. The force is proportional to the product of two masses: F ~ m1m2.
The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ (m1m2)/(d^2)
What happens to the force of attraction between two planets when the masses of both are doubled? The force doubles. The force quadruples. The force increases by 16. The force remains the same
The force quadruples
Newton's universal law of gravity tells us that F=G*(m1m2)/d2. Newton's second law tells us that a=Fnet/m. With a bit of algebraic reasoning find your gravitational acceleration toward any planet of mass M a distance d from its center. Express your answer in terms of the variables M, d, and appropriate constants. How does this equation tell you whether or not your gravitational acceleration depends on your mass?
a= GM/(d^2) This equation shows that the acceleration is dependent upon the gravitational constant times the mass of the planet divided by the distance squared. that m cancels out. Therefore the only mass affecting your acceleration is the mass M of the planet, not your mass.
Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________. greater than your normal weight at rest equal to your normal weight at rest less than your normal weight at rest
greater than your normal weight at rest.
Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________. greater than your normal weight at rest equal to your normal weight at rest less than your normal weight at rest
less than your normal weight at rest.
Which of these animals has a quicker stride? giraffe mouse horse cat
mouse
Imagine that Earth had an identical twin planet, "Farth", which is twice as far away from the Sun as Earth is. Compared to the force of gravity that Earth exerts on the Sun, how strong is the force of gravity that Farth exerts on the Sun? one-fourth as strong one-half as strong the same strength twice as strong
one-fourth as strong
Torque= Lever Arm x Force. Calculate the torque produced by a 46-N force when a pipe extends the length of the wrench to 0.44 m.
τ = 20 N*m
A kilogram is a measure of an object's ________. force weight mass gravity
mass
An object is lifted from the surface of a spherical planet to an altitude equal to the radius of the planet. As a result, which of the following changes in the properties of the object take place? mass increases; weight decreases mass decreases; weight decreases mass increases; weight increases mass increases; weight remains the same mass remains the same; weight decreases mass remains the same; weight increases mass remains the same; weight remains the same
mass remains the same; weight decreases.
Suppose the Sun suddenly shrunk, reducing its radius by half (but its mass remaining the same). The force of gravity exerted on the Earth by the Sun would _________. decrease by half remain the same double quadruple
remain the same
A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 25-cm mark. From this information, the mass of the meterstick is 1 kg. 1/4 kg. 3/4 kg. 1/2 kg. none of the above
1 kg
Punch Taut is a down-on-his-luck heavyweight boxer. One day, he steps on the bathroom scale and "weighs in" at 236 lb. Unhappy with his recent bouts, Punch decides to go to a different planet where he would weigh in at 118 lb so that he can compete with the bantamweights who are not allowed to exceed 118 lb. His plan is to travel to Xobing, a newly discovered star with a planetary system. Here is a table listing the planets in that system: Name Mass ( Mearth) Radius ( Rearth) Tehar 2.1 0.80 Loput 5.6 1.7 Cremury 0.36 0.30 Suven 12 2.8 Pentune 8.3 4.1 Rams 9.3 4.0 In this table, the mass and the radius of each planet are given in terms of the corresponding properties of the earth. For instance, Tehar has a mass equal to 2.1 earth masses and a radius equal to 0.80 earth radii. If the acceleration due to gravity on the earth is 9.8 m/(s^2), what is the acceleration due to gravity on Rams?
5.7 m/s^2
If the polar ice caps of Earth were to melt, the oceans would be deeper. Strictly speaking, what effect would this have on Earth's rotation?
If all the polar ice caps of Earth melted and the oceans became deeper, the rotation of Earth would slow down by a very small amount. It's similar to an ice skater who, when they put their arms out, slows them down, whereas if they have their arms in or up, they spin faster. Since the polar ice caps are along the Earth's axis of rotation, it's like having the arms in, and it spins at the speed it does. But if the polar ice caps melt, I think it would cause the water to move around the Earth and level out (the Earth would have it's arms out in the figure skater analogy). It would not cause much of a difference in the rotational speed, but it would cause a very small one.
How does the thickness of paint sprayed on a surface change when the sprayer is held twice as far away? It is ¼ as thick. It is twice as thick. It is the same thickness. It is ½ as thick.
It is 1/4 as thick.
What is a gravitational field, and how can its strength be measured? It is a force field with direction and magnitude at every point in space. It's strength is the force on a test mass. It is a force field in empty space with direction and magnitude equal to the inverse square of the mass of a test mass. It is a force field on any body with mass. Its strength is the force per unit mass on a test mass. It is a force field on a body with mass, with direction and magnitude equal to the inverse square of the distance to a test mass.
It is a force field on any body with mass. Its strength is the force per unit mass on a test mass.
If Earth shrank, but there was no change in its mass, then what would happen to your weight at the surface? It would increase. It would decrease. It would stay the same. It would decrease at first and then increase.
It would increase.
Angular Momentum= mvr If the force of friction that keeps a 90-kg person sitting on the edge of a horizontal rotating platform when the person sits 1.6 m from the center of the platform and has a tangential speed of 6.4 m/s , what will be the person's angular momentum?
L= 920 (kg*m^2)/s
Punch Taut is a down-on-his-luck heavyweight boxer. One day, he steps on the bathroom scale and "weighs in" at 236 lb. Unhappy with his recent bouts, Punch decides to go to a different planet where he would weigh in at 118 lb so that he can compete with the bantamweights who are not allowed to exceed 118 lb. His plan is to travel to Xobing, a newly discovered star with a planetary system. Here is a table listing the planets in that system: Name Mass ( Mearth) Radius ( Rearth) Tehar 2.1 0.80 Loput 5.6 1.7 Cremury 0.36 0.30 Suven 12 2.8 Pentune 8.3 4.1 Rams 9.3 4.0 In this table, the mass and the radius of each planet are given in terms of the corresponding properties of the earth. For instance, Tehar has a mass equal to 2.1 earth masses and a radius equal to 0.80 earth radii. Which planet should Punch travel to if his goal is to weigh in at 118 lb?? Refer to the table of planetary masses and radii given to determine your answer. Tehar Loput Cremury Suven Pentune Rams
Pentune
Why do the astronauts in the Space Shuttle float around? The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness. There is no gravity in the Space Shuttle because it is completely enclosed and shielded from the effects of gravity due to the Earth. There is no gravity in the Space Shuttle because it is too far away from the center of the Earth.
The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness.
Object A has three times as the mass of object B. Identical forces are exerted on the two objects. Which statement is true? The speeds of the two objects are equal after 2 seconds. The acceleration of object B is three times that of object A. The speed of object A is three times that of object B after 3 seconds. The accelerations of the two objects are equal.
The acceleration of object B is three times that of object A
Why would a bowling ball and a small marble fall down to the surface of the Moon at the same rate? The force of gravity is proportional to the object's mass. The force of gravity on an object in a vacuum is zero. The force of gravity is the same for each object.
The force of gravity is proportional to the object's mass.
How does the gravity in the Space Shuttle compare with the gravity on Earth's surface? The gravity in the Space Shuttle is much smaller than the gravity on Earth's surface. The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth. The gravity in the Space Shuttle is much larger than the gravity on Earth's surface.
The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.
Predict how the upward force exerted on the feet by the scale will compare to the weight if the elevator is moving downward at a constant speed. The upward force on the feet will exceed the weight. The upward force on the feet will be less than the weight. The upward force on the feet will be equal to the w
The upward force on the feet will be equal to the weight.
Predict how the upward force exerted on the feet by the scale will compare to the weight of the person if the elevator is moving upward at a constant speed. The upward force on the feet will be less than the weight. The upward force on the feet will exceed the weight. The upward force on the feet will be equal to the weight.
The upward force on the feet will be equal to the weight.
Predict how the upward force exerted on the feet by the scale will compare to the weight if the elevator is accelerating downward. The upward force on the feet will be equal to the weight. The upward force on the feet will exceed the weight. The upward force on the feet will be less than the weight.
The upward force on the feet will be less than the weight.
Predict how the upward force exerted on the feet by the scale will compare to the weight if the elevator is accelerating upward. The upward force on the feet will be equal to the weight. The upward force on the feet will exceed the weight. The upward force on the feet will be less than the weight.
The upward force on the feet will exceed the weight.
A parachutist is falling toward the ground. The downward force of gravity is exactly equal to the upward force of air resistance. Which statement is true? The velocity of the parachutist must be zero. The velocity of the parachutist is decreasing with time. The velocity of the parachutist is increasing with time. Review Lesson 1 in the tutorial for additional help. The velocity of the parachutist is not changing with time.
The velocity of the parachutist is not changing with time.
Where do you weigh more: at the bottom of Death Valley or atop one of the peaks of the Sierra Nevada? Why? You weigh more in Death Valley because more atmosphere pushes down on you. You weigh more on the summit, because the higher you go, the harder you fall. You weigh more in Death Valley because you are closer to the center of Earth. You weigh more on the summit because the air buoys you up less.
You weigh more in Death Valley because you are closer to the center of Earth.
Give an example of when your weight is greater than mg. Give an example of when your weight is zero. Your weight is greater than mg when you are in free fall. Your weight is zero when you are accelerating upward. Your weight is greater than mg when you are accelerating downward. Your weight is zero when you are in free fall. Your weight is greater than mg when you are on top of a mountain. Your weight is zero when you are in free fall. Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.
Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.
Punch Taut is a down-on-his-luck heavyweight boxer. One day, he steps on the bathroom scale and "weighs in" at 236 lb. Unhappy with his recent bouts, Punch decides to go to a different planet where he would weigh in at 118 lb so that he can compete with the bantamweights who are not allowed to exceed 118 lb. His plan is to travel to Xobing, a newly discovered star with a planetary system. Here is a table listing the planets in that system: Name Mass ( Mearth) Radius ( Rearth) Tehar 2.1 0.80 Loput 5.6 1.7 Cremury 0.36 0.30 Suven 12 2.8 Pentune 8.3 4.1 Rams 9.3 4.0 In this table, the mass and the radius of each planet are given in terms of the corresponding properties of the earth. For instance, Tehar has a mass equal to 2.1 earth masses and a radius equal to 0.80 earth radii. If acceleration due to gravity on the earth is g, which formula gives the acceleration due to gravity on Loput? g(1.7/5.6) g((1.7^2)/5.6) g((1.7^2)/(5.6^2)) g(5.6/1.7) g((5.6^2)/(1.7^2)) g(5.6/(1.7^2))
g(5.6/(1.7^2))
Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was moving upward at constant velocity? Downward at constant velocity? More compressed while moving upward and while moving downward There would be no more compression and no more expansion for both upward and downward motion. More compressed while moving upward and less compressed while moving downward Less compressed while moving upward and more compressed while moving downward
There would be no more compression and no more expansion for both upward and downward motion.
Punch Taut is a down-on-his-luck heavyweight boxer. One day, he steps on the bathroom scale and "weighs in" at 236 lb. Unhappy with his recent bouts, Punch decides to go to a different planet where he would weigh in at 118 lb so that he can compete with the bantamweights who are not allowed to exceed 118 lb. His plan is to travel to Xobing, a newly discovered star with a planetary system. Here is a table listing the planets in that system: Name Mass ( Mearth) Radius ( Rearth) Tehar 2.1 0.80 Loput 5.6 1.7 Cremury 0.36 0.30 Suven 12 2.8 Pentune 8.3 4.1 Rams 9.3 4.0 In this table, the mass and the radius of each planet are given in terms of the corresponding properties of the earth. For instance, Tehar has a mass equal to 2.1 earth masses and a radius equal to 0.80 earth radii. After Punch Taut travels to Pentune, what actually happens to his mass and his weight? mass increases; weight decreases mass decreases; weight decreases mass increases; weight increases mass increases; weight remains the same mass remains the same; weight decreases mass remains the same; weight increases mass remains the same; weight remains the same
mass remains the same; weight decreases.
