A force is applied on a 250g lab cart at rest. The cart starts moving along a straight track. The graph describes the relationship between the force applied on the cart over time. A student reasons that at t = 8 s, the cart must be moving in the opposite direction of its initial push because during the 6 to 8 s time interval, the cart experiences the greatest change in force. |(Positive force is to the right, negative force is to the left)