Question

Short Answers Conceptual Questions 1. (a) A lead cylinder floats in mercury at 0oC. Will the...

Short Answers Conceptual Questions
1. (a) A lead cylinder floats in mercury at 0oC. Will the lead float higher or lower if the temperature is raised? (b) Freezing a can of soda will cause its bottom and top to bulge so badly that the can will not stand up. What has happened?
2. (a) Is it possible to boil water at room temperature (20oC) without heating it? Explain. (b) Explain why burns caused by steam at 100oC on the skin are often more severe than burns caused by water at 100oC?
3. (a) Distinguish between the concepts of thermal energy, temperature, and heat. (b) Write a short paragraph explaining why fish live through cold winters even when the ponds are frozen over.
4. (a) Write a short paragraph distinguishing between conduction and convection. Give two examples of each. (b) From a molecular point of view, explain why evaporation is a cooling process. What cools?
5. (a) Distinguish between a transverse wave and a longitudinal wave. Give examples of each. (b) What is wave interference, and the two types of wave interference?
6. (a) What kind of waves do you think will travel down a horizontal metal rod if you strike its end (i) vertically from above (ii) horizontally parallel to its length? (b) A tire swing hanging from a branch reaches nearly to the ground (as shown below). How could you estimate the height of the branch using only a stopwatch?

7. (a) Describe how you could estimate the speed of water waves across the surface of a pond. (b) What evidence can you give that the speed of sound in air does not depend significantly on frequency?
Think and Rank
8. (a) Rank the magnitudes of these units of thermal energy from greatest to least: (i) 1 calorie, (ii) 1 Calorie, (iii) 1 joule. (b) From greatest to least, rank the energy needed for these phase changes for equal amounts of H2O: (i) from ice to ice water, (ii) from ice water to boiling water, and (iii) from boiling water to steam.
9. (a) Rank the speed of sound in through the following media from fastest to slowest: (i) air, (ii) steel, (iii) water. (b) All the waves shown in Fig. 1 below have the same speed in the same medium. Use a ruler and rank these waves from greatest to least for: (i) amplitude, (ii) wavelength, (iii) frequency, and (iv) period.

Fig. 1
Problems
10. (a) A volume of helium gas has a temperature of 10°C. The same gas twice as hot has a temperature of
A) 10°C. B) 12°C. C) 283°C. D) 293°C. E) none of the above
10. (b) What would be the temperature of 50 g of 20°C water mixed with 80 g of 40°C water?
A) 24.6°C B) 26.9°C C) 27.6°C D) 28.3°C E) 32.3°C
11. (a) As a train of water waves goes by, a piece of cork floating on the water bobs up and down one complete cycle each second. The waves are 2 m long. What is the speed of the wave?
A) 0.25 m/s B) 0.50 m/s C) 1.0 m/s D) 2 m/s E) 4 m/s
11. (b) The range of human hearing is about
A) 10 Hz - 10,000 Hz. B) 20 Hz - 20,000 Hz. C) 40 Hz - 40,000 Hz.
D) all of the above, depending on the person
12. (a) Suppose you sound a 1056-Hz tuning fork when you strike a note on the piano and hear 2 beats/second. You tighten the piano string very slightly and now hear 3 beats/second. What is the frequency of the piano string?
A) 1053 Hz B) 1054 Hz C) 1056 Hz D) 1058 Hz E) 1059 Hz
12. (b) The fundamental frequency of a violin string is 440 Hz. The frequency of its second harmonic is
A) 220 Hz. B) 440 Hz. C) 880 Hz.

Homework Answers

Answer #1

1.

(a)

The ability of a medium like mercury to provide bouyancy/flotation is dependent on its density relative to what's trying to float in it. Raise mercury temperature, you lower its density, making the lead relatively more dense than it had been before. Lead floats lower.

(b)

Soda is mostly water.
Water is unique in that it's the only known substance to expand when in freezes. This is why ice cubes float.
Because the water in the soda is freezing, the soda expands, causing the bulge in the top and bottom of the can, and occasionally exploding, popped, or leaking cans.

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