Urgent physics questions (1 Viewer)

[Validity]

1. how did hertz measured wavelength for his experiment with the spark? [solved]

2. For semiconductors, is an Electric field necessary for neighboring electrons to move into the positively charged holes? [solved]

3. What's bohrs 1st postulate? i thought it was "only certain electron orbits are stable and electrons in it don't lose energy" [solved]

4. Wave-particle or wave-matter duality for de Broglies proposal or is it the same? [solved]

5. what were paulis contribution? was it the 4th quantum number which explains hyperfine splitting

6. did chadwick use conservation of charge or just momentum and energy?

7. need critical mass of fissionable material to create a self sustaining reaction?

8. i don't understand why projecting 2 balls to same heights but different ranges is affected only by the initial velocity? could someone explain thanks

9. Why does standing upright parallel to acceleration give a black out? isnt the apparent weight more than the true weight thus the force is acting upwards so shouldn't the blood be going to the head and causing a redout?

10. do we have to know the equations for linear velocity, angular velocity and thrust?

11. For application of keplers laws of period equation, How do we know when to use SI units or the AMU and Years?

12. Is the speed of light constant for ALL frames of references (non-inertial and inertial)? or just inertial?
[solved]

13. Do we need to know the thought experiments to calculate time dilation etc. [solved]

14. Is it mesons or muons for the evidence of time dilation and length contraction?[solved]

15. Why was gold used for rutherfords experiment

 

[kman16]

1. With the assistance of a parabolic mirror, Hertz created standing waves. This allowed him to measure the wavelength of the wave and hence work out the speed using v=fl. He found v to be very close to c (speed of light), confirming Maxwell's prediction that all electromagnetic waves travel at the speed of c.

2. The neighbouring electrons will move into the positive charged holes regardless of an electric field

 

[Validity]

so for 2.
no potential difference needs to be supplied ?

 

[GoldyOrNugget]

3. electrons in an atom orbit in stationary states of stability and do not emit energy in these states. Sounds like what you've got.

4. Wave-particle duality. Matter is composed of particles after all.

 

[Validity]

bump

 

[Ichiii]

5. Pauli contribution was the 4th quantum number which was the spin quantum number. This solved the hyperfine splitting where the energy of an electron is slightly different for the two spin directions. which you said.
He also contributed on his Exclusion Principle where he stated that no two electrons can have the same set of quantum numbers in an atom

6. Well he would have to use all of the conversation laws wouldn't he? But the answer is Conservation of momentum and energy in this context.

7. Critical mass is the smallest mass needed to produce a sustaining chain reaction since there must be a balance of the production and loss of neutrons.

 

[GoldyOrNugget]

8. It can be explained mathematically. Derive the conditions for constant maximum height, substitute into the range equation, and you should see that velocity is the only variable (I'm assuming this works)

9. Think about it in terms of your blood having inertia. As you accelerate upwards, your blood 'lags behind' in your feet. It does not rush to your head.

10. Linear velocity, yes. Angular velocity, no. I don't think there's a formula for thrust -- it's just the reaction force from Newton's laws e.g. expelling gases in a rocket produces thrust.

 

[dawooddaman]

11. Nope can be sec, hours or day
12. Yes in ALL frames of references
13. Not understand the Q. there a difference between qualitative and quantitative data
14. Muons

 

[Validity]

11. Nope can be sec, hours or day
12. Yes in ALL frames of references
13. Not understand the Q. there a difference between qualitative and quantitative data
14. Muons

For 11. how do we know what units to use and when?
and for 13. i mean as in like to prove the equations for the dilation etc.

 

[kiinto]

8. If two balls achieve the same height they must have had the same Uy value (Initial vertical velocity). Furthermore, they will have the same time of flight, as time of flight is only affected by vertical velocity. This means that for them to have a different range, the must have had a different horizontal velocity (x = Ux*t).

11. As far as I know, all calculations require SI units.

12. ALL frames of reference (i.e. both)

13. To calculate time dilation, no. But you will need to know at least one.

14. Muons, but also atomic clocks flown by jet around the earth.

 

[Danstar2]

8. i don't understand why projecting 2 balls to same heights but different ranges is affected only by the initial velocity? could someone explain thanks

We know that the two balls have to reach the ground at the same time when dealing with projectile motion and a constant downward uniform acceleration. The range will be different depending on the equation S = ut where s = horizontal displacement, u = horizontal velocity and t = time. With a higher initial velocity the ball will have a higher horizontal velocity than the other ball thus, u will increase. Thus displacement will increase proportional to u.