Why is it difficult to observe an exoplanet directly through a telescope?
A. It is hard to see exoplanets against the blackness of space.
B. Exoplanets are small compared to their parent star, so they reflect only a small portion of the star's light.
C. Exoplanets tend to be far away from their parent stars, making it hard to get both the star and the exoplanet in the telescope's field of view.
D. Exoplanet atmospheres absorb too much light
Answer: B
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You find a coin resting on your physics book cover and notice that when you open the cover, the coin slips exactly when the cover reaches 25 degrees above the horizontal. What is the coefficient of friction between the coin and book cover?
A. 0.20 B. 0.23 C. 0.37 D. 0.47 E. The question cannot be answered without knowing the coin's mass.
What is the Kuiper Belt?
A. an enormous aggregate of gas and dust from which the Solar System was formed B. a large belt containing asteroids in a gap between the orbits of Mars and Jupiter C. a swarm of comet nuclei in a huge shell surrounding the Sun and planets D. a disklike swarm of icy objects that lies from near the orbit of Neptune to past Pluto's orbit
Two vectors lying in the xy plane are given by the equations 
and 
. The value of 
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B.
C.
D.
E.
In this figure, why is the kinetic energy gained by the falling ball equal to the change of potential energy? (Assuming no loss of energy due to friction.)
a. Energy conservation requires that the total energy remains constant. In this example, the total energy is either in the form of kinetic energy or potential energy. b. This follows from momentum conservation. c. Both a. and b. d. Because the total energy decreases as the ball falls. e. Because the total energy increases as the ball falls.