As in the case of unlike magnetic poles, unlike electric charges a. attract each other. b. repel each other. c. exist in pairs. d. do not interact.  

Space-time metric ds2= -dt2+at2dx2+bt2dy2+ct2dz2 (a)how does the area of a rectangle with vertices at ( x=0, y=0, z=0 ), (1,0,0 ), ( 0,1,0 ) and (1,1,0 ) changes with time? (b) if a photon moving in the x direction starts from the origin at t=1, when does it reach x=l? (ds=0 for the trajectory of a photon.) (c) the proper time for a particle is defined by cd=ds. what is the proper time for a particle to move along the trajectory ( x(t)=t, y(t)=0, z(t)=0 ) from t=0 to 1 ? what is the condition on the parameter a so that the velocity of the particle never exceeds the speed of light ?

What are chlorofluorocarbons and what impact do they have on the atmosphere?

The passage that directs air to the lungs is called a. diaphragm. b. larynx. c. bronchi. d. pharynx.