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.

The great sandini is a 60.0-kg circus performer who is shot from a cannon (actually a spring gun). you don’t find many men of his caliber, so you him design a new gun. this new gun has a very large spring with a very small mass and a force constant of 1100 n/m that he will compress with a force of 4400 n. the inside of the gun barrel is coated with teflon, so the average friction force will be only 40.0 n during the 4.00 m he moves in the barrel. at what speed will he emerge from the end of the barrel, 2.50 m above his initial rest position?