A ball that is attached to a string travels in a horizontal, circular path, as shown in Figure 1. At time t0 , the ball has a speed v0 . The forces exerted on the ball at t0 are represented by the free-body diagram, as shown in Figure 2. At a later time t1 , the tangential speed of the ball is increased to 2v0 . What is the magnitude of the force that the ball exerts on the string at time t1 ?