Need more help with conceptual physics questions..please

Question

answer what you can :)

1. A mass attached by a light spring to the ceiling of an elevator oscillates vertically while the elevator ascends with constant acceleration. Is the period greater than, less than, or the same as when the elevator is at rest? why?

2. If a mass-spring system and a simple pendulum are vibrating 'in sync' on earth, would they still vibrate 'in sync' on Mars, where the pull of gravity is weaker than on our planet? If so, why? If not, which one would have a higher frequency on mars?

3. Which of the characteristics of a sound wave (amplitude or frequency) is most closely related to musical pitch? to loudness?

4. In describing the size of a large ship, one uses the expression 'it displaces 20,000 tons.' What does this expression mean? Can the weight of the ship be obtained from this information?

5. A rigid lighter-than-air balloon filled with helium cannot continue to rise indefinitely. why not? what determines the maximum height it can attain?

6. A very smooth wooden block is pressed against the bottom of a container of water so that no water remains under the block? will this block rise to the surface when it is released?

7. You have a drink that you want to cool off. you could put in 100g of ice or 100g of water, both at 0 degrees C. which one would be more effective in cooling your drink?

8. freezing cells can kill them by causing it to burst. Why does a cell burst when frozen?

9. Equal masses of two different gases placed in containers of equal volume at equal temperature must exert equal pressures, true or false?

It's a lot, I know, but help would really be appreciated

Answer 1

My conceptual toughts on the questions.

Answer to 5. The air gets thinner as you get farther away from the earth. Eventually the air and helium will get to the same density level and the ballon will no longer continue to rise.

Answer to 6: Depends on if the wood floats to begin with? If it does it would rise if not it would stay when released.

Answer to 7: The liquid at 0 degrees C would cool the drink faster due to more surface area around the drink to effectively cool it.

Answer 2

This aren't direct answers, but rather hints at understanding the answer.

4. The displacement refers to the water that is being replaced or pushed away as by the sunken part of the ship. The relationship between the displaced water and the weight of the ship is governed by Archimede's principle, which I hope you'll look up.

7. When solids melt to liquids, it actually stays at the same temperature until ALL of the solid absorbs enough heat to melt to liquid. When it's already all liquid, then heat starts to increase temperature.

8. Why does ice float on top of water? It's less dense. But it's the same amount of mass, so how did it get less dense? Density is mass divided by volume. Now consider that cells are mostly water.

9. Ideal gas law - PV = nRT. now note that n is not mass, but rather molecules of the gas. Different gases have different masses per molecule.

Answer 3

1. Even though the elevator is moving, it is not accelerating, so the net force (gravity) on the spring will be the same regardless of whether the elevator is moving at a constant speed or just still.  Because of this, the period will be the same.

2. Yes.  Both experience the same force.  On mars, it will oscillate in sync, but with a lower period.  

3. Frequency, or vibrations per time is associated with pitch.  (Hertz)

Amplitude, or energy, is associated with loudness.  

4. I'm not sure about this one, but i'll guess.

20,000 tons is probably the weight of the total volume of the bottom of the ship that is part underwater.  

..

5.  Gravitational force is inversely proportional to the distance squared.   In other words, the force decreases dramatically the higher the balloon gets till the point that the upward buoyant force is equal to the downward gravitational force.

6. No.  I"ve never really learned this, but i've played with metal blocks in the lab, and it definitely sticks to the surface. I think it's because of suction, but don't take my word on this.

7. Ice, if you're putting it INTO the drink.  Although the liquid at the same temperature has more kinetic energy/ mol than ice, so it'll be less efficient than ice to absorb heat.  

Water, if you're SURROUNDING the glass with it because of increased surface area and effective transfer of heat.  

8. There are two reasons:

- Water expands when frozen.

- The cell wall/membrane has expanded beyond its elastic potential.

9. False.  Equal mass doesn't necessarily mean equal moles.    If the number of moles are the same, then it'll be true.  

yay!

Answer 4

I agree with the person above that you should read the book and you will find the answer. These are basically application of the concepts you have learnt. Give it a thought and you will get it for sure.

for example,

3) Amplitude = loudness

and frequency = pitch

7) Ice will be more effective in cooling the water (we use it all the time) because of Latent heat of fusion. When water reaches 0 deg. C, it doesn't freeze instantly, it absorbs more coolness (so to speak) and freezes to form ice. That extra energy is latent (hidden). Now to melt it (in case with warm liquid that you would like to cool), the ice will absorb that extra heat that is required for the phase change (solid to liquid = known as latent heat of fusion). So 100 g of ice will absorb more heat from the liquid and consequently cool it more.

The concept is similar when liquid goes to vapour and it is known as Latent heat of vapourization.

8) when you freeze water, it tends to expand because ice occupies more volume than liquid water (you can do this by looking up densities of ice and water from wikipedia or something and converting the same mass to volume). Cells are mainly water and when they freeze they burst just like pipes burst when water freezes in them.

9) PV = nRT

P = nRT/V ==> for two gases everything but "n" i.e. moles will be different because you are given equal masses and molar mass are different (therefore number of moles will be different because n = mass / molar mass).

Hence it is false.

So, I ll let you think about the rest and have fun!!

Answer 5

I think you should spend your time finding the answers yourself instead of typing the questions into Yahoo Answers.