Physics Quiz #4...CH 10

What is the ratio of escape speed from Earth to circular orbital speed? Ignore air resistance.

1.41

Escape speed from Earth is any speed equal to or greater than __________.

11.2 km/s

A stone is thrown upward at an angle. What happens to the magnitude of the vertical component of its velocity as it rises? As it falls?

It decreases while rising, but it increases while falling.

For orbits of greater altitude, is the period longer or shorter? Is the speed faster or slower?

The period is longer and the speed is slower.

The kinetic energy of a satellite remains constant when the satellite follows a __________.

circular path

The foci of the elliptical path for an Earth satellite are __________.

one at Earth's center and the other elsewhere

A projectile is launched upward at an angle of 70° from the horizontal and strikes the ground a certain distance downrange. For what other angle of launch at the same speed would this projectile land just as far away?

20°

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?

5 m, 20 m

How far does a projectile drop in 1 second? What is the speed needed for a projectile to orbit Earth?

5 m, 8 km/s

About how far below a straight-line path does a satellite in close Earth orbit fall in the first second of fall?

5 meters

How far below a straight-line path does a horizontally projected projectile fall in the first second of fall?

5 meters

A projectile is launched at 30° above ground level. What other angle at the same speed will result in the same range?

60°

How much time does it take for a complete revolution of a satellite in close orbit about Earth?

90 minutes

What exactly is a projectile?

An object that is projected by some means and continues in motion by its own inertia.

Is the sum of kinetic and potential energies a constant for satellites in circular orbits, in elliptical orbits, or in both?

Both

Who gathered the data that showed planets traveling in elliptical paths around the Sun? Who discovered elliptical orbits? Who explained them?

Brahe, Kepler, Newton

When air resistance is neglected, why does the vertical component of velocity for a projectile change with time, whereas the horizontal component of velocity doesn't change?

Gravity is a purely vertical force.

Why does the force of gravity change the speed of a satellite in an elliptical orbit?

Gravity slows the satellite as it moves away and speeds it up on its return.

At what part of an elliptical orbit does an Earth satellite have the greatest speed? The lowest speed?

Greatest nearest Earth; lowest furthest from Earth

How can a projectile "fall around the Earth"?

In a circular orbit around a spherical planet, the force and the fall are always toward the center. The projectile falls 5 m for every 8 km and so does Earth. A projectile can "fall around Earth" if the distance it falls matches the curvature of Earth. All of the above.

Do your answers to the preceding question depend on the angle at which the projectile is launched?

No

For an Earth satellite in circular orbit, list all the values that do not change.

Only speed, gravitational force, and distance from Earth

A stone is thrown upward at an angle. What happens to the horizontal component of its velocity as it rises? As it falls?

Rising or falling, it does not change.

For an Earth satellite in an elliptical orbit, list all the values that do change.

Speed, gravitational force, and distance from Earth

Why doesn't the force of gravity change the speed of a bowling ball as it rolls along a bowling lane?

The force is at a right angle to the motion.

Why doesn't the force of gravity change the speed of a satellite in circular orbit?

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?

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

What did Kepler discover about the periods of planets and their distances from the Sun?

The period squared was proportional to the distance cubed.

Kepler was the first to be credited for discovering that planets follow __________.

elliptical paths

he horizontal and vertical components of velocity for a projectile are __________.

independent of each other