Recent content by ak1948

I get P = 753 for the minimum tipping force. I don't think the answer in your book is right. Let x=1.4, y=1.6, w=1000N. Then the torque = (W/2) (x sin 30 + y cos 30) - P y cos 30. This gives P = (W/2) ( x/y tan 30 +1) = 753 for zero torque.

Does this make sense? The spacetime interval between two events doesn't change when you change from one inertial frame to another, although x and t do. If s^2 = 0, the measured time between events (t) is equal to the time required for light to travel the measured distance between the events...

To answer part 1, why don't you just directly solve your second equation? You have q1, q2, and you can easily find r.

Problem 2: I think you have this right. But I am not exactly clear as to what you have done. Define E as any convenient value. Let's call it zero; this is completely arbitrary. Since the velocity is 0 at the top, the energy is mgh at the top, so we also have to define h=0 at the top. At...

I guess the easiest way to say it is mgh + (1/2)mv^2 = E at every point. Where E is the same for every point. Since m and g are also the same for every point, you can calculate the change in v between any two points by the change in h. (Or if you needed to, the change in h by the...

The experimental setup for each of these cases is pretty much the same, isn't it? You apply a voltage and measure the current. Of course for b and d you have to do this in both directions and for c you have to find a way to keep the temperature constant.

The equation is incorrect. Are you looking for a force or an impulse? If an impulse, its just equal to the change in momentum of the mallet, which you can easily calculate since you know the kinetic energy of the mallet when it strikes (from conservation of energy). If you are looking for the...

no that's kinetic energy. centrifugal force is mv^2/r.

looks right to me.

You don't want work. You are looking for force, specifically the difference between the centrifugal force and the gravitational force.

2) Hallsofivy gave you the clue. K=0 (or nearly) at the top of the circle. You know how to find the difference in potential energy between the top and the bottom and the top and the starting point. Therefore you can find the kinetic energies and speeds at those points.

B is weber/m^2

No at the top of the loop it's moving. You just figured out how much potential energy you gave up getting there. So how much kinetic energy did you pick up if the total energy is unchanged?

1) The equation you used E= K+U is right. Let's not bring W into this. Remember E doesn't change in this frictionless problem. You showed you know how to find initial U at with respect to the bottom of the loop; how about with respect to the top of the loop. Obviously K is 0...

The weight at the end of the pendulum produces a torque. This is obviously mgr*cos(theta), where r is the length of the pendulum. To counter this torque, the minimum force needed is mg*cos(theta) if the force is directed perpendicularly to the rod.