A block of mass m is attached to an ideal spring with spring constant k, as shown below. The friction between the block and the surface is negligible. Initially, the block is at rest at position x = xi, and the spring is stretched. At time t = ti, the block is released from rest. The block speeds up until t = t, when it passes xf with speed Vf. In answering the following questions, Just before 1 = t 101 =0 consider system 1, consisting of the block k and spring, as indicated by the dashed line m shown at right. If, for these questions, the *= X X= X block and spring cannot be grouped together as a system, state so explicitly. During the interval from t; to t, is the net k work on system 1 by external forces positive, m negative, or zero? X= X X= X The net work on system 1 is positive. O The net work on system 1 is negative. O The net work on system 1 is zero. O The block and spring cannot be grouped as a system.The diagram is repeated below. Recall that initially, the block is at rest at position x = x;, and the spring is stretched. At time t = ti, the block is released from rest. The block speeds up until t = t, when it passes xf with speed Vf. System 1, consists of the block and spring. Just before 151 =0 as indicated by the dashed line shown at k right. m X= X X=X During the interval from t; to t, does 1= 1 the total energy of system 1 increase, k decrease, or stay the same? m O The total energy of system 1 increases. X= X X = X The total energy of system 1 decreases. O The total energy of system 1 stays the same. O The block and spring cannot be grouped as a system.Now consider system 2, consisting of the Just before 1 = 1 151 =0 block only, as indicated by the dashed line k in the diagram shown at right. If, for these m questions, the block alone cannot be treated as a system, state so explicitly. X= X X= X 1= 1 Recall that initially, the block is at rest at position x = xi, and the spring is stretched. k m At time t = t;, the block is released from rest. The block speeds up until t = t, when X= X X=X it passes Xf with speed Vf. During the interval from t; to t, is the net work on system 2 by external forces positive, negative, or zero? O The net work on system 2 is positive. O The net work on system 2 is negative. O The net work on system 2 is zero. O The block alone cannot be treated as a system.During the interval from t; to t , does the total energy of system 2 increase, decrease, or stay the same? The total energy of system 2 increases. O The total energy of system 2 decreases. The total energy of system 2 stays the same. O The block alone cannot be treated as a system