How much water at 20°C is needed to melt 1 kilogram of solid mercury at its melting point of ?39°C? (The heat of fusion of mercury is 2.8 cal/gram)
23.4 grams
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A mirror has a hole cut in it so that a light can shine through. Opposite the mirror is another mirror, which is parallel to the first. The light ray hits the second mirror with angle ?1, is reflected at an angle ?2 , and then is incident on the first mirror at angle ?3. At what angle to the normal, ?3, in terms of ?1, will the reflected ray then impact the first mirror?
1. ?/2 – ?1 2. ?1 3. ?/2 + ?1 4. –?1
We can be sure the particles in the rings of Neptune are very small because
a. the rings are faint in forward scattered light. b. the rings are bright in forward scattered light. c. only small particles are produced in comet impacts with larger moons. d. the magnetic field of Neptune would quickly force large particles out of the rings. e. the larger particles would be quickly destroyed by impacts with the shepherd satellites.
If you blow air between a pair of closely-spaced Ping-Pong balls suspended by strings, the balls will swing
A) toward each other. B) apart from each other. C) away from the airstream.
Which of the following is an almost reversible process?
a. The explosion of hydrogen and oxygen to form water. b. Heat transfer through thick insulation. c. The adiabatic free expansion of a gas. d. A slow isothermal compression of a gas. e. A slow leakage of gas into an empty chamber through a small hole in a membrane.