Recent content by per persson

Sorry I'm completely lost are you talking about example 1 or 2?

So the formula for emk for a circuit is where f_s is caused by non emf forces like a battery. E is the electricalfield inside the circuit? v is the velocity of the circuit and B is the external magnetic field. I have difficulty understanding E. There are two "types" of electrical field one...

But what is so special with the centre. I know it is easier to calculate but what makes the centre the point where we can just add potentials to get the total. Suppose b) gives potential Vo inside the sphere and the hemisphere gives V1 in the centre. Then the total potential is V=Vo+V1. But a...

Why is it legit to add the potential of the hemisphere to the potential inside sphere given by b and thus get the solution for c. The implications of this is really powerful and too good to be true. There has to be some restrictions when this method that solves c can be used.

Potential of the hemisphere or the potential given in b? I don't think it matters though since the solution is already given. My problem is why can we just add the potential of the hemisphere to the potential inside the sphere and thats the answer.

The sphere with charge Q is of metall and the question is what its potential is . a and b I've already solved but c is difficult conceptually. The answer is down below but I don't understand it. Here is the solution of c: So the contribution of the potential of the hemisphere is simply added...

I don't understand how why the derivative is continuous. Clearly there is a surface charge and by gauss law we should have

Above is the pages of the problems. T is the force caused by a cable. I'm still lost on how to determine if there is reactive moment or not when there are more than two supports. If I understand your method right you find an axis where reactive forces of two supports do not cause a torque...

In the picture below consider the plane where T_z and T_y of T lie and the plane where A_x and A_y lie. They intersect in a line which is parallel to the x-axis. The force 300lb and A_z causes a torque around this axis but it does not prevent the rotation around it thus there is a reactive...

Are you saying given a set of forces how to find an axis where there is no torque about it? I would just check if the action of line of the forces pass through the axis or are parallel to the axis.

I'm thinking a disc centered at z=0 that lies on the xy-plane. The only forces that will not cause the disc to spin are those for which the action of line passes through the z-axis and those which are parallel to the z-axis. Correct? Edit: Sorry it should say how can I determine from a diagram...

In the book engineering mechanics statics and dynamics Hibbeler says:" It should be noted that the single bearing supports in items (5) and (7), the single pin (8), and the single hinge (9) are shown to resist both force and couple-moment components. If, however, these supports are used in...

In r<a the potential is V_o. I don't understand why in a<r<2a, V(r)=V_o-\int^r_a E*dl. I would write V(r)=\int^r_a E*dl+\int^2a_\infty E*dl I dont know how to write math symbols here but I wrote question here...

I remember yes. I think I understand moment better know. Consider a beam that is fixed to the wall. The gravitational force on the beam causes a moment and where it is fixed to the wall prevents the rotation of the beam thus in a free body diagram we draw a moment there. But if beam is fixed at...