# Recent content by dvdqnoc

1. ### Force on electron from current-carrying wire

Homework Statement http://img236.imageshack.us/img236/5369/physxn6.png [Broken] Homework Equations F = IL x B F = QV x B The Attempt at a Solution Since I know I, L, Q, and V, I tried to work those into the two force equations... but I got no where. They dont give me B.
2. ### Tricky torque problem

Work is the change in kinetic energy. KEf - KEi, but since its at rest in the beginning, its KEf - 0, which is just w=KEf. Remember to consider rotational kinetic energy, because it is rotating. Good luck to you both!
3. ### Tricky torque problem

they give you 118 rpm. You have to convert that to angular velocity using factor label. You have time and final angular velocity, so you can find angular acc. using Vf = Vi + at where Vf=final angular vel, Vi = initial angular vel (which is 0 in this case), a=angular acc, and t=time. then...
4. ### Calculating final Velocity

well then i guess your initial approach is correct. the equation I gave might not work cuz i didnt read the part that said "avg velocity". I think your -61 is correct
5. ### Calculating final Velocity

I dont know why they gave you impulse, you can solve the problem with this equation: Vf = Vi + at where Vf=final velocity, Vi=initial velocity, a=acc. and t=time. Remember - the acc. is .8/.462 because F=ma, so a=F/m. Good luck!

Yes.
7. ### Frictionless Surface

Newton's 3rd law tells us that when you punch the wall, the wall punches back equally. In other words, with equal force. In other words, you don't punch the block with any more force than the wall punches you with. In other words, your punch's force and the wall's punching force are equal. So...
8. ### Two objects - when do they meet?

Homework Statement An object is thrown downward with an initial speed of 4 m/s from a height of 99 m above the ground. At the same instant, a second object is propelled vertically from ground level with a speed of 25 m/s. The acceleration of gravity is 9.8 m/s^2. At what height above...
9. ### Position when 2 objects pass each other

What I did didn't work. I kind just mushed stuff together. I might as well have said "I didnt know where to start" because I didnt.
10. ### Packaged dropped from Hot Air Balloon

well a is -9.8 because of gravity. Vi is 2.6, but its the opposite direction of falling. So what do I do with it? d is 19 m. I dont know how to use that equation because the Velocity is upward, but the object is falling DOWN.

First of all, you dont need to make a theoretical velocity because they cancel out in the end. Now... (2)(1/2 I w^2) + (1/2 m v^2) (2)(1/2) is 1. You know that w=v/r, so plug in v/r for w, and you get I(v/r)^2 + (1/2 m v^2) You know I, r, and m, so you get ((.08)V^2)/.3 + (1/2)(74)V^2 Do...