Recent content by asdff529

Homework Statement Initially there is a spherical charge distribution of with a radius ##R_0## and uniform charge density ##ρ_0##. Suppose the distribution expands spherically symmetrically such that its radius at time t is ##R_0 + V t##, where V is the velocity. Assuming the density remain...

My teacher gives me an explanation about this: A moving clock(observer B) runs slower actually means it is slower comparing to two stationary clocks at different locations. Does it have something to do with relativity of simultaneity? I also heard of Hafele-Keating experiment.And it comes out...

When the observer B is traveling at a very high speed, the observer A on the ground will record a time dilation. But at the same time,from the point of view of B, A is also traveling at a very high speed relative to B. Here comes the question:does that mean they both record the time...

A voltaic cell is composed with reactants and products in their standard states.So when it operates,the concentration of all substance must change,it should no be hold.Am i right?

I think what the resultant acceleration means is that A,which is acceleration of the whole system moving left or right I still get 3 unknowns,a,A and T,in two equations

Homework Statement Given that two masses are connected by a light string over a pulley.They are initial at rest.Suppose all the surfaces are smooth.Find the resultant acceleration of the system Homework Equations F=ma Fpseudo=-ma The Attempt at a Solution Suppose I let the resultant a be A,and...

Base on maxwell-boltzmann distribution,we can calculate the average velocity of gas molecule . i read a book and it proves like that average velocity=\int vf(v) dv I don't understand why we don't have to divide it by N because we should be calculating the average,but not the total. Would...

i almost forgot i can use the formula v^2-u^2=2as so v=sqrt(2rαS) ? and ω=αt or ω=v/R am i going right?

Homework Statement A mass m is tied with a light string,which it's another end is winded at a axle fixed at wall,in which it's radius is r. Assume there is no friction.The mass is released from rest and falls a distance S after time t. Find the moment of inertia of the axle.(represents I in...

If C is still near the X,the space near C will have positive charge.After C is removed and my finger is still touching the sphere,the two spheres will become neutral,am I correct?

it doesn't specify at what point body C is removed from the picture

um...if i treat the spheres as a big thing,this 'big thing' will become positively charged as it is charged by earthing.Then when these spheres are separated,since sphere X is the one touched by the finger,it will become positively charged.But i ain't sure what the charge of Y is. Also,the...

Suppose we have two insulated uncharged metal spheres,say X and Y, in contact with each other.A negatively charged object C is brought near X My first question is:Do all of the electrons move to the sphere Y since electrons are free to move? Then if X is touched momentarily with a finger,and...

but my teacher said if we use E=σ/ε0 and Q is kept constant,the electric field is independent of d. it seems that there is a contradiction,because E=V/d as well,where am i wrong?

There are two expressions of electric field between two parallel plates,say one carries Q and another carries -Q Then the electric field between them=σ/ε0 But there is another expression that E=V/d where d is their distance of separation What are the differences between them?And what are the...