Which of the following best describes a substance in which the temperature remains constant while at the same time it is experiencing an inward heat flow? A) a gas under constant volume.
B) a liquid.
C) a solid.
D) a substance undergoing phase change.

One form of energy can be another type of energy. a. created to form b. transformed into c. destroyed and then created to form

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Two masses are connected by a rope that hangs over a pulley as shown below. the pulley is a uniform cylinder of radius 푅=0.381meters and mass 푀=3.1푘푔. initially 푚"is on the ground and 푚#rests 2.5 meters above the ground. if the system is released, use conservation of energy to determine the speed of 푚#just before it strikes the ground. assume the pulley bearing is frictionless.