# Search results

1. ### Destruction of a planet

Nah, I don't believe that, I think it moreover will be like putting something cold in boiling water, it creates a low-temperature region that will slowly warm up and mix with the sun. I don't really see how it could spiral into our sun? It would seem to me that it would obtain an elliptical...
2. ### A ball shot at an angle

Sorry for the late reply: Just sketch an arrow making 30 degrees with the horizontal. Then project the vector onto the x-axis and that's your x-component. It's that easy. Magnitude of the vector in the x-direction is as you described, 5.4cos30. The direction of motion with respect to the...
3. ### A ball shot at an angle

Unit vectors are a simple way of describing a 3d (or 2d) vector. Basically, you put everything that describes the x-direction together and put 'ex' with a vector sign over it behind it. Do thesame for the y-direction. In this case: the x-component of the speed is just 5.4cos(30), so that part...
4. ### Conservation of momentum

Those equations might not be so ridicuous after all. The total momentum is 40*m in the positive x-direction. Keep that in mind. So the total momentum in the y-direction is 0. The pucks do get a speed in the y-direction though, so these must be equal and opposite to make the total...
5. ### Need help with entropy question

Alright, you already showed us that delta U = 0, since it's an ideal gas. So Qin = -Won. In this case the Work on the gas is positive, the piston has to do work on the gas to compress it, so heat has to be removed from the gas, which follows fromthe formula. Won = - INT P dV ---> so Qin = INT...
6. ### Need help with entropy question

Sure. It says in the excersize that the gas is compressed slowly and isothermally, so there always is an equilibrium. nRT/V can be put into the integral, making Q = nRT * INT (dV/V) from V1 to V2. (Which makes Q = nRT *ln(V2/V1). Using relative volumes is enough here. Good luck!
7. ### Need Help in Physics

This one requires 1 formula and 1 law. Use s = 0.5*a*t^2 to estimate the speed both balls will have (will be identical). Then use the law of conservation of momentum. The baseball will take over the basketball's momentum and the basketball will take over the baseball's momentum, effectively...
8. ### Pre-AP physics help

cdhotfire has the golden tip. Split the vector into Vx and Vy and then look at how these change during the fall.
9. ### Lots of Trouble With Free-Fall

That's kind of basic, though I must admit I only got good at it recently. Just subtract the M*t from one side and add it to the other, with opposite signs. Always remember you may apply anything to any side of the equation, as long as you do it to the other side, too. So subtract it from one of...
10. ### I need a better understanding

https://www.physicsforums.com/showthread.php?s=&threadid=204 thats the thread with a lot of sites. If you want some explanation in general, tell me where you fail in understanding it. What is not clear for you, and so on. I'm sure there are lots of ppl here who are able to give you a better...
11. ### Magnetism and Tesla's

So you want to know the vertical component or what? If that is true, you could just use the cosinus or sinus of the angle (22 degrees).
12. ### Silly question about redshift, relativity

If I'm not mistaken, all galaxies were formed out of very very big gas clouds (or even a big big gas cloud formed as soon as the universe started to cool down), so you could also argue that early galaxies should be less dense.
13. ### The effect of mass on roller coaster cars

Alright... a = f / m f = m * g a = (m*g)/m = g. Add a cosinus or sinus and you'll have the exact amount. This all is thesame for each car though, it doesn't depend of it's weight. It has to be either friction or aerodynamics. And I am not into either of those. Strange problem!
14. ### Acceleration of Pail Problem

Yea prolly a typo
15. ### Problem - need direction

I am no expert at this since it's been 8 months since I last had magnetism, but I'll try to help. The sum of the forces must be 0. First, we need the part of the gravity that makes the cilinder roll, being cosinus(90-theta). This must equal the lorentz force. The magnetic field is uniform, and...
16. ### Hubble Ultra Deep Field

I recently saw a documentary on Discovery covering the Hubble telescope. At the very end of the program they said something about the next-generation Hubble, which (if they get the thing up somehow... \$-wise) will be positioned 1 000 000 kms from earth. Sounds good! They want to look at the...