AST 115 Ch. 4 HW

Visual Question 4.4 The diagram above shows a planet at four positions in its orbit. At which position does it have the greatest gravitational potential energy?

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Which of the cars is accelerating?

A car going around a circular track at a steady 100 miles per hour.

Newton showed that Kepler's laws are _________.

natural consequences of the law of universal gravitation

Visual Activity: Weight and Weightlessness in a Moving Elevator Part D- When you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale

In the formula E = mc^2, what does E represent?

the mass-energy, or potential energy stored in an object's mass

Vocabulary in Context: Describing Forms of Energy Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.

1. The light from Polaris travels through space in the form of radiative energy 2. Rapidly moving comets have more kinetic energy than slowly moving ones. 3. An apple contains chemical potential energy that your body can convert into other forms energy. 4. Nuclear fusion in stars converts some of the mass-energy of hydrogen nuclei into light and heat. 5. Due to its much higher density, water heated to 80 degrees (Celsius) contains more thermal energy than air at the same temperature. 6. An asteroid that is moving farther from the Sun is gaining gravitational potential energy.

Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?

Both will hit the ground at the same time.

Sorting Task: Temperature Scales Each of the following items states a temperature, but does not tell you whether the temperature is measured on the Fahrenheit, Celsius, or Kelvin scale. Match the items to the appropriate temperature scale.

F: A hot summer day might be 100. Ice cream is stored in freezers at 26 C: Water freezes into ice at 0 A typical room temperature is 24 Liquid water boils at 100 K: The coldest possible temperature is 0 Water boils into gas phase at 373.15

Key Concept: Distinguishing and Recognizing Newton's and Kepler's Laws Part B- Match the correct laws to the examples in which they apply. Use each law only once. Drag the words in the left-hand column to the appropriate blanks in the right-hand column.

For planets orbiting the Sun, period (p) and orbital distance explains why Earth orbits the Sun at a faster average speed than Mars. For any force, there is an equal and opposite reaction force tells us that, when you are pushing on a table, the table is pushing up on you with a force that precisely balances the force of your push. A line between a planet and its Sun sweeps out equal areas in equal times explains why Earth's orbital speed varies over the course of each year. An object moves at constant velocity if there is no net force acting on it explains why a spaceship with no forces acting on it will continue moving even if it has no fuel. Force equals mass times acceleration explains why applying a force to a baseball with your arm can cause the baseball to accelerate from rest to the speed at which it leaves your hand. The orbit of each planet is an ellipse, with the Sun at one focus explains why Earth's distance from the Sun varies over the course of each year.

Key Concept: Distinguishing and Recognizing Newton's and Kepler's Laws Part A- The six statements below represent Newton's three laws of motion and Kepler's three laws of planetary motion. Match each statement to the scientist (Kepler or Newton) associated with it. Drag the names in the left-hand column to the appropriate blanks in the right-hand column. The names can be used more than once.

Kepler: The orbit of each planet about the Sun is an ellipse with the Sun at one focus. Kepler: A planet moves faster in the part of its orbit nearer the Sun and slower when farther from the Sun, sweeping out equal areas in equal times. Kepler: More distant planets orbit the Sun at slower average speeds, obeying the precise mathematical relationship p2=a3. Newton: An object moves at constant velocity if there is no net force acting upon it. Newton: Force = mass x acceleration Newton: For any force, there is an equal and opposite reaction force.

The energy attributed to an object by virtue of its motion is known as _________.

Kinetic Energy

A net force acting on an object will always cause a change in the object's _________.

Momentum

Ranking Task: Pairs of Gravitationally Interacting Objects The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left.

Strongest to Weakest: Sun Earth Moon Asteroid Hydrogen Atom

Visual Question 4.3 The diagram above shows a planet at four positions in its orbit. At which position does it have the greatest angular momentum?

The angular momentum is the same at all four points.

Visual Activity: Weight and Weightlessness in a Moving Elevator Part C- 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

A rock held above the ground has potential energy. As the rock falls, this potential energy is converted to kinetic energy. Finally, the rock hits the ground and stays there. What has happened to the energy?

The energy goes to producing sound and to heating the ground, rock, and surrounding air.

Visual Activity: Weight and Weightlessness in a Moving Elevator Part E- 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.

Radiative energy is _________.

energy carried by light

As an interstellar gas cloud shrinks in size, its gravitational potential energy:

gradually transforms into other forms of energy

Visual Activity: Weight and Weightlessness in a Moving Elevator Part A- 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

Visual Activity: Weight and Weightlessness in a Moving Elevator Part B- 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