# Recent content by blackwing1

1. ### Center of Mass and Wedge

Thanks for helping :D However, I still don't get it. What exactly is M_1, M_2 and V_1 and V_2 in this case, and how do the initial equations arrive at the conclusion through the arrows? Could you please elaborate? I kind of see how the math works, but I don't know how it arrives at the...
2. ### Center of Mass and Wedge

Homework Statement A large wedge rests on a horizontal frictionless surface. A block starts from rest and slides down the inclined surface of the wedge, which is rough. During the motion of the block, the center of mass of the block and wedge. a. does not move. b. moves horizontally with...
3. ### Thermodynamics heat engine Question

It's water, so with a density of 1, the answer should still be what I got.
4. ### Thermodynamics heat engine Question

Homework Statement A 1500kW heat engine operates at 25% efficiency. The heat energy expelled at the low temperature is absorbed by a stream of water that enters the cooling coils at 20 degrees C. If 60L flows across the coils per second, determine the increase in temperature of the water...
5. ### Forces and Pulleys

No, you were right. Let me rephrase that. Let m1 be the mass on the left, and m2 the mass on the right. Let T1 be the tension holding up m1 and T2 be the tension holding up m2. So would T1 also be the force that applies the counterclockwise torque, and T2 the clockwise torque? I always...
6. ### Forces and Pulleys

Thanks for answering. Well, the equation you gave (T1-T2 = Ia/r^2) is the same as the one I got, just multiplied by -1 on both sides (T2-T1 = -Ia/r^2). In your case, you are designating T2 as negative and thus counterclockwise. Shouldn't the acceleration still be negative then? As for the...
7. ### Forces and Pulleys

Homework Statement A pulley has a moment of inertia of 5.0 kg*m^2 and a radius of 0.5m. The cord supporting the masses m_1 and m_2 does not slip, and the axle is frictionless. Find the acceleration of each mass when m_1 = 2.0 kg and m_2 = 5.0 kg. Homework Equations F=ma, Fr=I(alpha)...
8. ### Acceleration in respect to power, and a KE/momentum problem.

Thanks for the help. I figured them out. Kind of surprised I hadn't seen the answers sooner. Pretty obvious in hindsight. :biggrin:
9. ### Acceleration in respect to power, and a KE/momentum problem.

I was doing the IPhO F=ma test from 2008 and couldn't get these two questions. Question 1 Homework Statement A car has an engine which delivers a constant power. It accelerates from rest at time t = 0, and at t = t_0 its acceleration is a_0. What is its acceleration at t =2t_0? Ignore energy...

Thanks. :D
11. ### Deriving the Formula for Gravitational Potential Energy

Hey guys, Do any of you happen to know how to derive the formula for General gravitational potential energy (not the mgh one) without using calculus? Thanks. Just in case you guys want to know, I'm trying to derive the equation for this: http://xkcd.com/681_large/. I've got most of it, but I...
12. ### Xkcd (angular momentum problem)

I was reading xkcd and wondering if spinning in a counterclockwise way (on the northern hemisphere) would actually steal some of earth's angular momentum and slow it down a bit. Is it possible or does this violate conservation of momentum?
13. ### Are newton's three laws applicable everywhere?

Are newton's three laws applicable everywhere in the universe?
14. ### Charged black hole

Black holes do have charge because the angular momentum, mass, and charge of any particles that are sucked in are retained by the black hole itself.
15. ### Light and gravity

actually, you're also wrong about the energy not escaping. energy is slowly leaked out of black holes, and the black holes themselves destingerate after immensly long period of time. An, the light affected by gravity is explained in the local frame/closed rocket acceleration thought expiriment...