Recent content by mstud

Hi! I am looking for a very rigorous book on some of the topics covered in Calculus of Multiple Variables. My University uses the last part of Adams "Calculus: a complete course" and I found the presentation therein more fit for people needing to know enough to perform the calculations than for...

#14 oli4

Thanks a lot!

I see I must solve: (m+M)v=Mv_2 +m(-v_2) for v_2 When I posted the original question I had tried to "conserve" kinetical energy and solve it for velocity. :lol:

Homework Statement a) At the skating rink, a girl of 35 kgs slides at a velocity of 3.0 m/s against her father. Her father, who is standing with his skates in the direction of motion, has a mass of 90 kgs. He takes hold of her and they slide together across the ice. Friction is ignored. What...

Thanks a lot for your correction and advice! :smile:

Homework Statement The speed of a projectile is measured by shooting it into a sanbox hanging in 6.00 m long threads. The projectile has a mass of 12.0 g, and the sandbox has a mass of 3.00 kg. The projectile ends up laying still in the sandbox. Thus the sandbox and the projectile moves as...

What the margin of safety would imply is that to protect the red LED from exceeding its reverse voltage rating, the forward drop of the LED has to be a little lower than 3.6 V e.g. 3.4 V or something (in this case), or am I mistaken here? If that was the case, what about the other way, is it...

Very good suggestion ! I think I liked this one best... Practically, it would not be difficult to set up. And the plan still will show that one have understood much of the properties of diodes. (I see why it is important to check for a safety margin, so that the reverse current does not...

Good suggestions :) Thanks a lot! Maybe I'll choose the last and most fancy way...

Oh, yes, that's true! Then it is: Voltage=\frac{W}{q}=\frac{3.68 \cdot 10^{-19} J}{1.602 \cdot 10^{-19} C}= 2.297 \approx 2.3 V Thanks again...

Uh, hmm, not quite sure of my reasoning. The charge comes from recombination of electrons and holes in the diode. Each of these have a charge of 6.242×10^{18} e= 1.602×10^{−19} C and -6.242 ×10^{18} e = -1.602×10^{−19} C, respectively. But how can I know how many does recombine for the diode...

OK. thank you :)

One more question from the same topic: Problem: An LED emits photons with the energy of 3.68 \cdot 10^{-19} J and the wavelength 540 nm. What is the least voltage which must be applied to the diode for it to emit those photons? My question: How to find voltage based on this information...

I think it sounds to easy too...The problem is from a book in "Physics & Technology" for the 12th year of school. (I'm in the 13th now, actually)