Hel plzz I'm confused If the acceleration due to gravity is 9.8 m/s^2 and you drop a rock off the top of a building. It takes 4.5 s to hit the ground. How tall is the building?​

The rigid beam is supported by the three suspender bars. bars ab and ef are made of aluminum and bar cd is made of steel. if each bar has a cross-sectional area of 450 mm2, determine the maximum value of p if the allowable stress is (σallow)st = 200 mpa for the steel and ( σallow)al = 150 mpa for the aluminum. est = 200 gpa and eal = 70 gpa.

An air-standard stirling cycle operates with a maximum pressure of 600 psia and a minimum pressure of 10 psia. the maximum volume of the air is 10 times the minimum volume. the temperature during the heat rejection process is 100°f. calculate the specific heat added to and rejected by this cycle, as well as the net specific work produced by the cycle. use constant specific heats at room temperature. the properties of air at room temperature are r

Inside of a windmill or a dam is a that is used to transform one type of energy into electrical energy. a. motor b. generator c. transformer d. power pack