S. A box is in an elevator that is moving up and getting slower. a} Is the work done by gravity positive, negative, or zero? b) Is the work done by the normal force positive, negative, or zero? 6. A 6 kg block is being pulled to the right across a horizontal table by a cable that makes a 20 angle above the horizontal. The tension in the cable is ZON and the coefficients of kinetic and static friction are 0.15 and 0.36, respectively. If the block starts from rest, what will be its speed 5.0 seconds after the rope starts pulling? 7. A ball is thrown straight upwards. Consider five points during the ball's motion: i) while It is being thrown and is still in contact with the person's hand, ii) after it leaves the person's hand and is rising upward, iii} when it is at the very top of its motion, iv) when It is on the way down but is not yet in contact with the person's hand, and v) while it is being brought to rest by the person who is catching It. For each of these situations, state whether the ball's acceleration is up, clown, or zero. 8. A block is moving to the right across a frictionless surface at a speed of 7 m/s when it passes point A. At point B, which is 8.6m to the right of point A, the surface becomes rough (coefficient of kinetic friction 0.23). What is the total time it takes for the block to move from point A to the point where Is comes to rest on the rough surface? B A __ frictionless rough