Which of these errors are random? a. trial time is recorded with a watch that is a half second off each minute. b. the door to a dark room is opened while an x-ray is being developed. c. a balance was not zeroed before being used to measure the mass of an object. d. a student misreads the temperature on a thermometer. e. the use of a cell phone interferes with the radio frequency of an electronic device. check all that apply.

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.

Suppose a diode consists of a cylindrical cathode with a radius of 6.200×10^−2 cm , mounted coaxially within a cylindrical anode with a radius of 0.5580 cm . the potential difference between the anode and cathode is 260 v . an electron leaves the surface of the cathode with zero initial speed (v initial=0). find its speed vfinal when it strikes the anode.

The solid that is formed and usually sinks to the bottom of a solution is the