The magnitude of the drag force of air resistance on a certain 20kg object is proportional to its speed. if the object has a terminal speed 80m/s, what is the magnitude of the drag force of an object when it is falling with a speed 30m/s?

In a system with only a single force acting upon a body, what is the relationship between the change in kinetic energy and the work done by the force? answers: work is equal to the change in kinetic energy.work depends on the square of the change in potential energy.work is equal to the negative of the change in kinetic energy.work is equal to the square of the change in kinetic energy