Recent content by goodboy

A particle moves in the xy plane under the constraint that its velocity vector is always directed towards a point on the x-axis whose abscissa is some given function of time f(t). Show that for f(t) differentiable, but otherwise arbitrary, the constraint is nonholonomic...

put a iron beside a magnet,then we konw the iron would be attracted toward the magnet.but where does the kinetic energy of the iron come from?

calculate the MOI. first assume the coodinat of the axis is (x,y,z).and the distance from points to axis are known as ri.then the MOI =Σmiri^2 or ∫ρiri^2dl do you think it is right?

thank you very much,my first language is chinese.i'm not good at english,don't laugh at me . there is no problem in your interpretation.

How to get this conclusion if we know the magnetic moment m,and the magnetic induction B.then the force is who can tell me how to get this.thanks very much

momentum is a vector,in your first equation "2"means what? my solution like this: P1sin(14)+P2cos(14)=P P1cos(14)=P2sin(14) P3=√(2mfs) there P1 is the momentum of the truck , P2 is the momentum of the sport car. P is the final momentum of both vehicles m=m1+m2...

english is my second language,if there are some wrong in the sentence ,don't laugh at me :redface: dig a columniform cavity in a infinity uniformity magnetic medium.the cavity's radius is r and the high is h,and the axis of the cavity parallels the direction of magnetization M in the...

a problem.put a conductor in a electric field .then we konw that in the conductor ,the positive charge will move along with the direction of the electric field,and the negative charge will move along against the direction of the field.then at all point in the conductor ,the external field+the...

20.2=9.81/2*t^2,=>t=2.03 or 20.2 = 19.90792t - 9.81/2*t^2