Ch. 10 Homework

Why does the vertical component of velocity for a projectile change with time, whereas the horizontal component of velocity doesn't? A. Gravity is a purely vertical force. B. Air resistance can be ignored. C. The projectile has horizontal inertia but not vertical inertia. D. The projectile has vertical inertia but not horizontal inertia.

A. Gravity is a purely vertical force.

A. From greatest to least, rank the initial PEs of the balls relative to the ground below. Rank from greatest to least. To rank items as equivalent, overlap them. B. From greatest to least, rank the initial KEs of the balls when tossed. Rank from greatest to least. To rank items as equivalent, overlap them. C. From greatest to least, rank the KEs of the balls when hitting the ground below. Rank from greatest to least. To rank items as equivalent, overlap them. D. From greatest to least, rank the times of flight while airborne. Rank from greatest to least. To rank items as equivalent, overlap them.

A. Greatest: Middle: A, B, C Least: B. Greatest: Middle: A, B, C Least: C. Greatest: Middle: A, B, C Least: D. Greatest: B; thrown highest Middle: A; thrown mid Least: C; thrown lowest

A. From greatest to least, rank them by their vertical components of velocity. Rank from greatest to least. To rank items as equivalent, overlap them. B. From greatest to least, rank them by their horizontal components of velocity. Rank from greatest to least. To rank items as equivalent, overlap them. C. From greatest to least, rank them by their accelerations when they reach the top of their paths. Rank from greatest to least. To rank items as equivalent, overlap them.

A. Greatest: B ; 20m/s, 53 degrees 2nd: C ; 10m/s, 45 degrees 3rd: A ; 10m/s, 37 degrees Least: D ; 10m/s, 30 degrees B. Greatest: B ; 20m/s, 53 degrees 2nd: D ; 10m/s, 30 degrees 3rd: A ; 10m/s, 37 degrees Least: C ; 10m/s, 45 degrees C. Greatest: Middle: A, B, C D Least:

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. Satellites orbit at a height where gravity is essentially zero. D. Air resistance counteracts the effects of gravity.

A. The force is at a right angle to the velocity.

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

B. The force of gravity is perpendicular to the motion in a circular orbit but not in an elliptical orbit.

Kepler was the first to be credited for discovering that planets follow ____________. A. curved paths B. elliptical paths C. circular paths D. parabolas

B. elliptical paths

When a ball is thrown upward at an angle, what happens to the vertical component of its velocity as it rises? As it falls? Suppose that air resistance can be neglected. A. It increases while rising and while falling. B. It increases while rising, but it decreases while falling. C. It decreases while rising, but it increases while falling. D. Rising or falling, it does not change.

C. It decreases while rising, but it increases while falling.

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

D. 11.2 km/s

About how far below a straight-line path does a satellite in close Earth orbit fall in the first second of fall? A. Depends on the projected speed B. 10 meters C. Zero meters D. 5 meters

D. 5 meters

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

D. Speed, gravitational force, and distance from Earth

The foci of the elliptical path for an Earth satellite are __________. A. both outside Earth B. both inside Earth C. one atop the other at Earth's center D. one at Earth's center and the other elsewhere

D. one at Earth's center and the other elsewhere