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).
What will be an ideal response?
23.4 grams
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Why does the electric force dominate at the atomic scale while the gravitational force dominates on the large scale that includes the solar system and beyond?
a. Atoms have no net charge, making electrical forces within atoms negligible. b. There is no gravitational force within atoms, because the law of gravitation applies only to large objects. c. Atomic particles have too little mass for gravitational attraction to compete with electric forces. d. At large distances, individual charges have essentially no effect since, overall, atoms are electrically neutral. e. Both c. and d.
Consider an atom of carbon in which the nucleus contains six protons and seven neutrons. What is its atomic number and atomic mass number?
A) atomic number = 6; atomic mass number = 13 B) atomic number = 6; atomic mass number = 7 C) atomic number = 13; atomic mass number = 6 D) atomic number = 7; atomic mass number = 13
Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground. What is the round third prong for?
a. It serves as a backup to the hot wire. b. Nothing electrical, it is for mechanical sturdiness. c. It connects the case of the appliance directly to ground for safety purposes. d. It lets the appliance run if the neutral wire breaks.
A floating leaf oscillates up and down two complete cycles in one second as a 10-meter long water wave passes by. What is the wave's speed?
A) 2 m/s B) 10 m/s C) 20 m/s D) 40 m/s E) more than 40 m/s