For a satellite in orbit around Earth, the product of its speed times the distance from the center of Earth has the same value when the satellite is at the perigee, its closest approach to Earth, and at the apogee, its furthest point from Earth
Is the product the same at other points on the orbit? Why?
No. According to Kepler's second law, equal areas are swept in equal times. For a short time interval, this translates into the product of the perpendicular component of radius times the speed times one-half of the time interval. Since the velocity and the radius are perpendicular to each other only at those two points, the product has that value only at those two points.
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A child is riding a merry-go-round which completes one revolution every 8.36 s. The child is standing 4.65 m from the center of the merry-go-round
(a) What is the tangential speed of the child? (b) What is the magnitude of the centripetal acceleration of the child?
A shift in the position of an emission line of an element toward the red or blue is produced by ____
a. atoms that become ionized b. electrons that transfer from a high energy level to a low energy level c. electrons that transfer from a low energy level to a high energy level d. the intensity of agitation of atoms in a hot gas e. the motion of an object toward or away from the observer
The sky is dark at night:
A) because the stars in the Milky Way are far away. B) because the Sun is on the other side of Earth. C) because there are far fewer stars on the night side of Earth. D) because all the light from all the objects in the universe hasn't arrived here yet. E) because the quasars are too far away from Earth for their light to have arrived here.
Asteroids which could possibly collide with the Earth at some time in the future are known as
A) killer asteroids B) Earth-crossing asteroids C) Armageddon asteroids D) potentially hazardous asteroids