1. Newton's law of gravity states that the force attracting two bodies, with masses M₁ and M₂ and separated by a distance R, depends on
   (A) (M₁ + M₂) / R.
   (B) M₁ x M₂ / R.
   (C) (M₁ + M₂) / R².
   (D) M₁ x M₂ / R².
   (E) (M₁ + M₂) x R².

2. The inverse-square law has the form F ~ 1 / R². (Here, "~" means "is proportional to") Therefore,
   (A) F increases by a factor of 4 if R increases by a factor of 4.
   (B) F increases by a factor of 16 if R increases by a factor of 4.
   (C) F decreases by a factor of 4 if R increases by a factor of 4.
   (D) F decreases by a factor of 16 if R increases by a factor of 4.
   (E) F goes to zero when R is zero.

3. Astronauts in a spacecraft orbiting about the Earth are weightless because
   (A) they are out of the Earth's gravitational field.
   (B) they are falling toward the Earth with the same acceleration as the spacecraft.
   (C) the Moon's gravity balances the Earth's gravity.
   (D) the Sun's gravity balances the Earth's gravity.
   (E) there is no gravity in outer space.

4. Which of the following statements is not correct?
   (A) An object in motion stays in motion unless acted upon by a force.
   (B) Newton's theory of gravity explains the planetary motion.
   (C) Every action has an equal and opposite reaction.
   (D) An object in circular orbit is constantly accelerating.
   (E) There is no gravity in outer space.

5. What defines a chemical element?
   (A) the number of electrons
   (B) the number of protons
   (C) the number of neutrons
   (D) the number of protons plus electrons
   (E) the number of protons plus neutrons

6. What is "absolute zero"?
   (A) the temperature at which water freezes
   (B) the temperature at which alcohol freezes
   (C) the temperature at which particles stop moving
   (D) zero degrees Fahrenheit
   (E) the temperature at which the University of Illinois closes

7. Which of the following has the most energetic photons?
   (A) gamma rays
   (B) X-ray
   (C) visible light
   (D) ultraviolet radiation
   (E) radio waves

8. Which of the following photons travels at the fastest speed?
   (A) gamma rays
   (B) X-ray
   (C) visible light
   (D) radio waves
   (E) they all travel at the same speed

9. The radiation from a star can be approximated by a blackbody curve. The apparent color of a star is determined by the wavelength at the peak of the blackbody curve. Therefore,
   (A) a blue star is hotter than a red star.
   (B) a blue star is cooler than a red star.
   (C) a blue star and a red star have the same temperature.

10. The spectrum of a blackbody depends only on its
    (A) magnetic field.
    (B) mass.
    (C) size.
    (D) age.
    (E) temperature.

11. Which of the following has the longest wavelength?
    (A) X-ray
    (B) gamma rays
    (C) visible light
    (D) ultraviolet radiation
    (E) radio waves

12. The blackbody radiation produced by a human body peaks at wavelengths in
    (A) the X-ray.
    (B) the ultraviolet.
    (C) the visible.
    (D) the infrared.
    (E) the radio.

13. Blackbody radiation depends on only temperature. If a blackbody is heated, it will become
    (A) bluer and dimmer.
    (B) bluer and brighter.
    (C) redder and dimmer.
    (D) redder and brighter.
    (E) don't know.

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Last updated September 15, 2001

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