Recent content by davo789

Pulsars accrete surrounding matter onto their surface. The strong magnetic field of the neutron star funnels the matter onto the poles of the star, and bright hotspots are created on the surface. If a neutron star has nothing to accrete, there are no hotspots, and there is no pulsar.

Looks fine to me!

These things often are!

Excellent, yes it does. So you should be able to calculate how much energy the student has gained, and you know how long it took...

If you lift a weight up into the air, what (other than height) are you giving it? If you drop it, it gains kinetic energy, but where does that energy come from? Sorry that it appears I'm taking a really roundabout route with this; I'm trying to get you to come up with the answer!

It's not brilliantly worded, but I think the clue is when it says that the 'crate *rests* on a horizontal surface'. i.e. it isn't moving. That should give you some info about the friction force.

But why is it hard work going upstairs, but not down them?

The table is symmetric, and you can assume that its mass acts from the centre of the tabletop. If you draw yourself a diagram you should see what's going on. Let me know if you don't!

So power is in Watts, which is Joules per Second. What does the student gain when (s)he runs upstairs?

What is the difference between speed and velocity?

The question you need to ask is why does the table tip up at all?

Now I see! That seems fine.

Usually questions like this are asking if you are looking down onto it (if the proton is at the origin, you are at +z). Also, I thought the question says that the B field is is in a +z direction?

Yep :-) What direction did you get, out of interest?

For the cross product