A particular type of fundamental particle decays by transforming into an electron e- and a positron e+. Suppose the decaying particle is at rest in a uniform magnetic field of magnitude 3.95 mT and the e- and e+ move away from the decay point in paths lying in a plane perpendicular to . How long after decay do the e- and e+ collide? Assume an electron and a positron are non-relativistic.

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?