The work done on the system by gravity is W = -ΔU, whether you are moving the stone up or down a gravitational potential, you just get either a positive or negative answer. When you were performing the calculation of the work you should have noted that F.x is the kinetic energy, thus:
F(xf-xi)...
When considering work, you must be careful whether you are talking about the work done on the system or the work done by the system. Both these meanings are subject to how you wish to define work, both are equally valid but you must stick to the same one. Your first statement describes the...
If half the volume of the block was below the boundary (5cm below) the block would have a density half way between that of oil and water (i.e 0.8 g/cm^3). From the density you could easily calculate the mass, try using the same argument for the numbers in your question.
Imagine the radiation leaving the sun as the surface of an expanding sphere, calculate the surface area of this sphere when it reaches the earth's surface (i.e a sphere with a radius equal to the distance between the sun and the earth). By considering what proportion of the total surface area...
This is just a thought that might simplify things a lot, the frequency of the wave describes how many times the wave passes a point per second, in this case an antinode. Also, each time the wave passes an antinode it has completed one full cycle from peak to trough and back to peak again.
Re: Speed
Got confused there, thought Stratosphere had asked the question originally. ViralRiver already gave the relevent equation (s=d/t) you ( or ViralRiver really) need to rearrange that for t.
You already have the answers you need, G is a well known physical constant, get it from a textbook or find it online. And as for the mass of the rocket, equate the equations given by chrisk and you will discover why it is irrelevent.
I didn't really know where to post this but i thought it could be a sociological discussion so...
I was reading through some of the threads in the general astronomy and cosmology section and there was something in a thread on the likelihood of extra terrestrial existence, something about it...
I could swear i have, although when i started thinking about it could happen i got confused. You can probably tell i'm a newbie as there must be some really simple explination to this problem. It might be a bit hard to explain without a diagram, but imagine a metaphorical one with the Sun on...