# Recent content by Mr.Amin

1. ### Electric field inside hydrogen atom.

The term "A" is probably going to be composed of two parts that add together. Try thinking about how to use a combination of step functions (or delta functions) to represent the electron and proton. Arfken has a little bit of material on this. If you have not had delta or step functions, I will...
2. ### Uncertainty principle

delta_r is your delta_x. The speed of the electron is not relativistic. (at least I don't remember it to be) Use the momentum to get your kinetic energy. Then convert units.
3. ### Battery provides a potential difference problem

Normally what you would do is integrate the current flowing from the battery to the capacitor. This means taking into account the resistance of the wires and anything in between the capacitor and battery. But if you haven't had this, LET CHEAT! We really don't need to know all the minutia...
4. ### Battery provides a potential difference problem

good job. Don't forget your units. Now remember that the charge entering the one side of the capacitor has to equal that returning to the battery from the other side. Have you learned about time decay of capacitors yet?
5. ### Battery provides a potential difference problem

Can't see the image. But let's start with how much charge IS in the capacitor? Write out the equation, and tell me. I will be online for another 10 minutes. We can solve this in 5 minutes.
6. ### A thought regarding angular acceleration, gravity, and weight.

FYI Don't know how much vector formalism you post-ers are into but writing down "centrifugal force" as F = -m*OMEGA x (OMEGA x R) gives you the forces of interest. Here OMEGA is you angular velocity vector, and R is the radial vector. Do the calc (pad and paper) and you will get the nice...
7. ### A thought regarding angular acceleration, gravity, and weight.

A very good first go. The centrifugal force in Ohio points "south." This is a question we normally give our undergrads in intro physics. Usually our question also asks "Why are space shuttles and rockets launched close to the equator?" If you plot out the centrifugal force felt by an object from...
8. ### Diameter and resistance

Good for you!
9. ### Diameter and resistance

First solve for the variable you are looking for and put it on one side. Keep your knowns on the other side. Remember that A stands for area, and area is related to wire diameter. I am online for a bit, so give it a go. DON'T FORGET YOU UNITS!
10. ### Force and angle

Newton V, good basic question. As you may have learned from your intro class, forces are represented by vectors. This is because they have magnitude (strength) and direction. What you should do 1) draw a picture of the problem. 2) Draw the force diagram, 3) break the forces into components, in...
11. ### Maximum attainable coefficient of static friction

Fair enough. Let's assume that the front tires "barely" leave the ground. This implies the rear tires DO NOT slip. Now since you know that the vehicle starts from rest, (1) what does the position equation look like? (2) From a term in this equation what term says anything about...force?
12. ### Maximum attainable coefficient of static friction

The knowledge that the front tires are lifted indicates torque which is directly related to the static friction acting on the tires. If the figure tells you the angle of lift, what missing information can you compute to determine average acceleration?
13. ### At what distance can your eye no longer resolve two headlights?

Your eye not diffraction limited of course. Usually problems do not hand you extra information in first/second year physics. What happens to light when it enters a lens? (Hint: The equation you are using works well for mirrors telescopes.)
14. ### Physics question

GOOD! Let's tackle question 1). How much energy is needed to get to maximum altitude? (Hint: use the potential energy equation.)
15. ### Physics question

GOOD! Let's tackle question 1). How much energy is needed to get to maximum altitude? (Hint: use the potential energy equation.)