Jack tries to place magnets on the door of his refrigerator. he observes that the magnets don’t stick. he guesses that the door of the refrigerator is made of a nonmagnetic substance. what stage of scientific investigation does his guess represent? a. ask questions b. construct a hypothesis c. explain the results d. make observations

The desk has a weight of 75 lb and a center of gravity at g. determine the initial acceleration of a desk when the man applies enough force f to overcome the static friction at a and b. also, find the vertical reactions on each of the two legs at a and at b. the coefficients of static and kinetic friction at a and b are ms = 0.5 and mk = 0.2, respectively

World class speed skaters can skate a 3,000-m course in about 4 minutes.what is their average speed for this course? a. 12.5 m/sb. 1.33 m/sc. 1.25 m/sd. 13.3 m/s

Atomic nuclei of almost all elements consist of