27. Suppose a 1000 -kg car moves initially at 3m/s, then at 6m/s, then its change in velocity is (0.5 Points) [4 positive negative 28. Suppose a 1000 -kg car collides with a tree. Its speed changes from 6m/s to 0m/s. The impulse on the tree is (0.5 Points). [4 positive negative

27. The change in velocity is calculated as final velocity minus initial velocity. In this case, it's 6 m/s - 3 m/s = 3 m/s. Since the result is positive, the change in velocity is **positive**.<br /><br />28. Impulse is calculated as the change in momentum, which is mass times the change in velocity. The car's change in velocity is 0 m/s - 6 m/s = -6 m/s. Since the change in velocity is negative, the impulse on the car is negative. However, the question asks about the impulse on the *tree*. According to Newton's Third Law, for every action, there is an equal and opposite reaction. Therefore, the impulse on the tree is **positive**.<br />