Beginning 156 miles directly east of the city of uniontown, a truck travels due south. if the truck is travelling at a speed of 31 miles per hour, determine the rate of change of the distance between uniontown and the truck when the truck has been travelling for 81 miles. (do not include units in your answer, and round to the nearest tenth.)

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?

Arigid tank is divided into two equal parts by a partition. one part of the tank contains 3 kg of compressed liquid water at 400 kpa and 60°c while the other part is evacuated. the partition is now removed, and the water expands to fill the entire tank. determine the entropy change of water during this process, if the final pressure in the tank is 40 kpa. use steam tables.

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.