Recent content by AJ Bentley

One more thing. Is the focal length of a convex mirror positive or negative? http://www.physicsclassroom.com/class/refln/u13l4d.cfm

1/ What makes you say that the object distance can't equal the focal length? 2/ Think about the significance of do being positive or negative - what does that mean?

Note that a + c = 4-2b and ab + bc + ac is the same as b(a + c) + ac So you can write X = b(4-2b) + ac. That's a quadratic that you can differentiate wrt b to find a maximum for X at a particular b. You can also find what ac must be from the same result. After that, a few substitutions gives...

you can work out what f is if you know R. Then try putting the image at each place offered to you as a possibility and work out where the object must be. (Obviously, start with the furthest distance - infinity)

The correct approach depends on what information you have. The basic equation is Hooke's Law F = -kx, which you use if you know the force and the extension of the spring. The other equation gives the Energy stored in a spring 1/2kx2 and sets it equal to the potential energy of a mass...

You lost a factor of 10 halfway. Otherwise good.

It doesn't look so bad... x3 is easy since 3s cancel a lot. Then x2 isn't too bad because 2*2 +2*1 = 6 which divides by 3 easily. It all simplifies nicely as you go along.:smile:

That isn't enough information to find the spring constant. There must be more to the question.

OK, so far, so good. So what's the answer?

Well, mg is the force due to gravity alone - which we call 'weight'. Is weight a g-force, or do we consider the other 'peculiar' forces (a) experienced on a ride the 'g-force' and leave weight out of it? Or is it all g-force? It's just semantics, but generally we'd consider weight part of the...

I would have though this had more to do with the blade shape than anything else. It looks like an aerodynamics question - an angle of attack of 15 degrees sound like an efficient sort of climb just short of a stall.

When I'm trying to explain something in layman's terms, I like to keep it simple. There are always sophisticated argument at the fringes of exploration that can be invoked as 'exceptions' to established rules. I consider it misleading to bring them up unless the OP has the tools to fully...

Question 6 is a bit ambiguous. The total reactance of the circuit is made up of a capacitive part and an inductive part. The result Xl - Xc is usually referred to as 'the reactance' qualified by the word 'capacitive' of 'inductive' depending on which is the larger. Anyway in this case - I think...

The situation begins with the switch closed. Before the switch is opened, the capacitor will charge up to some voltage, driven by both power supplies. You can calculate what that is. When the switch opens, it removes one of the voltage sources so that the capacitor begins to discharge into the...

Not quite. The river is flowing (right) at 7km/hr The swimmer moves (diagonally) at 8km/hr So you can calculate how fast the swimmer is moving directly across the river by drawing a triangle of velocities. Once you've got the speed it's easy.