# Recent content by xophergrunge

1. ### Strength of magnetic field required to balance gravitational force

Begin by looking at the equations for force due to a magnetic field and force due to gravity.
2. ### Mass places o that it is in equilibrium

So that what is in equilibrium? I believe you are missing part of the question.
3. ### Magnetic Field of A Toroid

I believe that is a mistake in the text. I think he meant it to be the vector r and not r hat, in which case the denominator would be cubed.
4. ### Circular Motion

Okay. So, what would happen if the centripetal force became greater than the weight?
5. ### Circular Motion

Do you mean maximum? The minimum speed would be zero.
6. ### Capacitor with dielectric

This should be D = ε0εrE Where are those 2's coming from?
7. ### Finding net force, acceleration and speed.

What forces are acting on the motorcycle? In what directions are these forces acting?
8. ### Tension and Pulleys Cannot understand this problem

Draw a free body diagram. How many tension forces T are there? What direction are these tensions in? Is it possible for them to "cancel" each other out?

Z≠2.5Ω.
10. ### Inductance problem

I get I = 0.707 A.
11. ### Inductance problem

You don't want to use V=IR, that doesn't take into account the reactance of your inductor. For a simple LR circuit V=IZ.
12. ### Spring motion

Do not set the first two equations equal to each other, they are not equal. The two forces acting on the mass, the weight and spring force, add to give the total force which will be zero when x=d.
13. ### Help with Torque Problem

The moment is a cross product, you haven't taken into account the angle between the moment arm and the force.
14. ### What is the angular speed in revolution per minute?

It seems like you are taking the correct steps. However, I get a different numerical answer than you do. Also, may I suggest that you don't plug all of those numbers in immediately, and just work with symbols until you have an expression for what it is you are looking for? It'll make the...
15. ### Related Rates (increasing cone radius question)

A variable to the first power's derivative is equal to one only when differentiating with respect to that variable. So, dh/dh=1, but dh/dt doesn't necessarily. You don't have to, but you would need to find dh/dt in terms of r and dr/dt and substitute that at some point. Personally I think it...