Agroup of students is making model cars that will be propelled by model rocket engines. these engines provide a nearly constant thrust force. the cars are light—most of the weight comes from the rocket engine—and friction and drag are very small. as the engine fires, it uses fuel, so it is much lighter at the end of the run than at the start. a student ignites the engine in a car, and the car accelerates. as the fuel burns and the car continues to speed up, the magnitude of the acceleration willa. increaseb. stay the samec. decrease