how fast must an object be moving in a given frame if its measured length in that frame is to be significantly different from its rest length?

Explain the comparisons between nature and packingtown that appears on pages 81 and 82 answer

Heterogeneous mixture with larger particles that never settle is

Point charges q1=+2.00μc and q2=−2.00μc are placed at adjacent corners of a square for which the length of each side is 1.50 cm . point a is at the center of the square, and point b is at the empty corner closest to q2. take the electric potential to be zero at a distance far from both charges. part a what is the electric potential at point a due to q1 and q2? express your answer with the appropriate units.