How do we most accurately measure the distance to the Moon?
A. We measure the lunar period and use Kepler's Third Law.
B. We measure its angular size and compare it to its actual diameter, which gives us its distance.
C. We bounce a pulse of light off the lunar surface and measure how long the trip takes.
D. We know how long it took Apollo astronauts to get there, and how fast the rocket traveled.
E. All of these choices provide equally accurate measurements.
Answer: C
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John and Linda are arguing about the definition of density. John says the density of an object is proportional to its mass. Linda says the object's mass is proportional to its density and to its volume. Which one, if either, is correct?
a. They are both wrong. b. John is correct, but Linda is wrong. c. John is wrong, but Linda is correct. d. They are both correct. e. They are free to redefine density as they wish.
A 5.0-C charge is 10 m from a small test charge. What is the magnitude and direction of the electric field at the location of the test charge?
What will be an ideal response?
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Mortimer pushes against a wall with a force of 10 newtons for a time of 5 seconds. How much work does Mortimer do on the wall?
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