Recent content by jianghan

I simplified my equations and now i can get the correct answer of 4.5v my equations are as follows assume R1//R3 is r IR1+IR2=6V 3IR2+3Ir=6V solve these to get R1-2R2=3r one more equation: IR1=3(3I)r → R1=9r so R1=3R1-6R2 R1=3R2 therefore IR1=4.5V

Homework Statement A battery has an emf of 6v. The battery is connected in series with an ammeter and a voltmeter.If a certain resistor is connected in parallel with the voltmeter,the voltmeter reading decreases by a factor of 3,and the ammeter reading increases by the sme factor. What is...

Actually in my solution for part 1,"total mass" means the combined mass of balloon and helium, i did exclude mass of the stone, that's why my answer agrees with the given answer. but thank you for your advice though

Oh,so your initial state actually refers to the state before the isothermal process,not the state just before the adiabatic process,i misunderstood it. now i understand your method. Thank you for answering so many questions, i think i learned a lot.

No,maybe the stones i used to tie my balloons to were all too heavy for this effect to be noticeable. anyway,for part 3,my solution is as follows maximum momentum=mballoon x at=0.0143 kgm/s net downward force=0.1264N time needed to "cancel" the upward momentum=0.0143/0.1264=0.113s time...

sorry one more question,if pressure before the isothermal expansion is the same as pressure after the adiabatic compression,and pressure changes in the first isothermal process,shouldn't pressure before and after the adiabatic process be different? why pi=pf ?

oh,ok,i always thought i needed to assume the initial length of the cylinder to be ho or something... so actually the information about the first isothermal expansion is not useful except telling me pressure is not changed? why for the adiabatic process pi=pf,i thought pi should be lower...

Thank you for suggesting a new method,i tried it,at first the equation looked promising but it turned out to be hugely complex and almost unsolvable as there were to many unknowns...

Homework Statement A party balloon(of mass 0.0025kg when empty) is filled with helium to a volume of 0.0045m3. it is tied to a small stone of mass 0.015kg by a light string of length 1.5m to prevent it from flying away. a child holds the balloon at ground level and then releases it...

oh i can get the correct answer now,i think the problem of my previous calculation is i used v value 0f 0.9999c to calculate γ(p=γmv),which i think is not accurate enough. later i used γ value i get from part 1 to calculate and get the correct p and B Thank you very much for your help!

oh i can get the correct answer now,i think the problem of my previous calculation is i used v value 0f 0.9999c to calculate γ(p=γmv),which i think is not accurate enough. later i used γ value i get from part 1 to calculate and get the correct p and B Thank you very much for your help!

Thank you for the clear explanation,now i have no doubt about this point.

ok,thank you all for your help! i think i can do both parts now. the second part ans is 424-457Hz which is relatively easy

can anyone tell me if the eqn R=mev/Bq for circular motion of charged particles in a magnetic field is valid in this relativistic case,i suspect that's where the problem in my solution lies

Homework Statement "Vibrato" in a violin is produced by sliding the finger back and forth along the vibrating string. The G-string on a particular violin measures 30cm between the bridge and its far end and is clamped rigidly at both points. its fundamental frequency is 197Hz (a) how far...