Astronomy Ch. 4 Homework

Suppose that two objects collide. Which of the following things is NOT the same both before and after the collision?

the total temperature of the objects

If the United States obtained all its energy from oil, how much oil would be needed each year?

1×10^13 liters

Which person is weightless?

A child in the air as she plays on a trampoline.

If you actually performed and compared the two trials chosen in Part C, you would find that, while the basketball and marble would hit the ground at almost the same time, it would not quite be exact: The basketball would take slightly longer to fall to the ground than the marble. Why?

Because air resistance has a greater effect on the larger ball.

Assume you have completed the two trials chosen in Part A. Which of the following possible outcomes from the trials would support Newton's theory of gravity? Neglect effects of air resistance.

Both balls fall to the ground in the same amount of time.

According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?

Earth's orbit would not change

Compare the energy of a 1-megaton hydrogen bomb to the energy released by a major earthquake.

Eearthquake/Ebomb = 5

Compare the Sun's annual energy output to the energy released by a supernova.

Esupernova/Esun ~ 10^11

Choose the correct definition and two examples of kinetic energy

Kinetic energy is the energy an object has due to its motion. Two examples are a var driving down the highway or the movements of the molecules of liquid in a cup of hot coffee.

Choose the correct definition and two examples of potential energy

Potential energy is energy that is stored. Two examples of potential energy are breakfast cereal, which has chemical potential energy, and a heavy book on the top shelf at the library, which has gravitational potential energy

Einstein's theory, like Newton's, predicts that, in the absence of air resistance, all objects should fall at the same rate regardless of their masses. Consider the following hypothetical experimental results. Which one would indicate a failure of Einstein's theory?

Scientists dropping balls on the Moon find that balls of different mass fall at slightly different rates.

In Part A, you found that your weight will be greater than normal when the elevator is moving upward with increasing speed. For which of the following other motions would your weight also be greater than your normal weight?

The elevator moves downward while slowing in speed

Suppose you are in an elevator car when the elevator cable breaks. Which of the following correctly describes what happens and why.

You float weightlessly within the elevator car because you and the elevator both begin to accelerate downward at the same rate

Consider the statement "There's no gravity in space." This statement is:

completely false

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them

decreases by a factor of 9

If you want to make a rocket turn left, you need to

fire an engine that shoots out gas to the right

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

When a spinning ice skater pulls in his arms, he spins faster because

his angular momentum must be conserved, so reducing his radius must increase his speed of rotation

Each diagram shows a single experimental trial in which you will drop a ball from some height. In each case, the ball's size, mass, and height are labeled. Note that two diagrams show a basketball, one diagram shows a bowling ball of the same size but larger mass, and one diagram shows a much smaller marble with the same mass as the basketball. You have a timer that allows you to measure how long it takes the ball to fall to the ground. Which pair of trials will allow you to test the prediction that an object's mass does not affect its rate of fall?

https://session.masteringastronomy.com/problemAsset/1101093/14/1101093_04.01_A.jpg

Consider again the experimental trials from Part A. This time, you wish to test how the size of an object affects the rate of its fall. Which pair of trials should you compare?

https://session.masteringastronomy.com/problemAsset/1101093/14/1101093_04.01_C.jpg

Why is Newton's version of Kepler's third law so useful to astronomers?

it can be used to determine the masses of many distant objects

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

less than your normal weight at rest

Choose the correct definition and two examples of radiative energy

radiative energy is energy in light. Sunlight carries this form of energy, as do other forms of light including X-rays and radio waves

Which of the following examples describes a situation where a car is experiencing net force?

the car is making a gradual turn

When you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale