PHSC 1001- Ch. 10 MasteringPhysics

The following diagrams all show the same star, but each shows a different planet orbiting the star. The diagrams are all scaled the same. (For example, you can think of the tick marks along the line that passes through the Sun and connects the nearest and farthest points in the orbit as representing distance in astronomical units (AU).) Rank the planets from left to right based on their average orbital distance from the star, from longest to shortest. (Distances are to scale, but planet and star sizes are not.)

You correctly identified the average orbital distances of the planets. Note that the line that passes through the Sun and connects the nearest and farthest points in the orbit is called the major axis, and half this line is the semimajor axis — which is the planet's average distance from the Sun.

A ball is thrown horizontally from a cliff at a speed of 10 m/s . You predict that its speed 1 s later will be slightly greater than 14 m/s . Your friend says it will be 10 m/s. Who is correct? A. your friend B. you

B

The positions of a satellite in elliptical orbit are indicated. Rank PE from greatest to least.

D, C, B, A

At what part of an elliptical orbit does an Earth satellite have the greatest speed? The lowest speed? A. Greatest nearest Earth; lowest furthest from Earth B. Lowest nearest Earth; greatest furthest from Earth C. It travels at a constant 8 km/s. D. Greatest at the focus inside Earth; lowest at the other focus

A

For an Earth satellite in an elliptical orbit, list all the values that do change. A. Speed, gravitational force, and distance from Earth B. Speed and gravitational force C. Gravitational force and distance from Earth D. Speed

A

The positions of a satellite in elliptical orbit are indicated. Rank KE from greatest to least.

A, B, C, D

The positions of a satellite in elliptical orbit are indicated. Rank acceleration from greatest to least.

A, B, C, D

The positions of a satellite in elliptical orbit are indicated. Rank gravitational force from greatest to least.

A, B, C, D

Escape speed from Earth is any speed equal to or greater than __________. A. 5 km/s B. 9 km/s C. 11.2 km/s D. 620 km/s

C

For an Earth satellite in circular orbit, list all the values that do not change. A. Speed and gravitational force only B. Speed only C. Only speed, gravitational force, and distance from Earth D. Speed, gravitational force, and distance from the Sun and Earth

C

A projectile falls beneath the straight-line path it would follow if there were no gravity. How many meters does it fall below this line if it has been traveling for 1 s? For 2 s? A. 10 m, 20 m B. 5 m, 10 m C. 10 m, 40 m D. 5 m, 20 m

D

Predict how the horizontal component of the velocity will change with time after the projectile is fired. A. It continuously increases. B. It continuously decreases. C. It first decreases and then increases. D. It first increases and then decreases. E. It stays constant.

E

The positions of a satellite in elliptical orbit are indicated. Rank momentum from greatest to least.

A, B, C, D

The positions of a satellite in elliptical orbit are indicated. Rank speed from greatest to least.

A, B, C, D

The positions of a satellite in elliptical orbit are indicated. Rank total energy (KE + PE) from greatest to least.

A=B=C=D

Predict how the vertical component of the velocity will change with time after the projectile is fired. A. It continuously increases. B. It stays constant. C. It first increases and then decreases. D. It continuously decreases. E. It first decreases to zero and then increases in the opposite direction.

E

The following diagrams are the same as those from Parts A and B. This time, rank the planets from left to right based on their average orbital speed, from fastest to slowest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

You correctly ranked the planets according to average orbital speed. Note that the pattern is another of the ideas that are part of Kepler's third law: Planets with larger average orbital distances have slower average speeds.

The following diagrams are the same as those from Part A. This time, rank the planets from left to right based on the amount of time it takes each to complete one orbit, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

You correctly ranked the planets according to how long they take to complete an orbit, which is what we call the orbital period. Note that the pattern is one of the ideas that are part of Kepler's third law: Planets with larger average orbital distances have longer orbital periods.

Why doesn't the force of gravity change the speed of a satellite in circular orbit? A. The force is at a right angle to the velocity. B. The inertia of the fast satellite is so great that gravity can be ignored. C. Air resistance counteracts the effects of gravity. D. Satellites orbit at a height where gravity is essentially zero.

A

Why is kinetic energy a constant for a satellite in a circular orbit but not for a satellite in an elliptical orbit? A. The force of gravity is perpendicular to the motion in a circular orbit but not in an elliptical orbit. B. Kinetic energy is constant for both orbits. C. Kinetic energy is not constant for a satellite in a circular orbit but it is for a satellite in an elliptical orbit. D. The force of gravity is perpendicular to the motion in an elliptical orbit but not in a circular orbit.

A

Each of the following diagrams shows a planet orbiting a star. Each diagram is labeled with the planet's mass (in Earth masses) and its average orbital distance (in AU). Assume that all four stars are identical. Rank the planets from left to right based on their orbital periods, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

Kepler's third law tells us that the orbital period of the planet is related to its average distance from the star, but not to the planet's mass.