6) You carry a 10 kg block up two flights of stairs. Each flight spans an elevation change of 4.2 meters. (10 points) 60 degrees a. How much work have you done during this exercise? W = F . S If F and S are in same direction then W is positive If F and S are in opposite direction then W is negative In this case, the force and distance are in the same direction. W = mgh = 10 x 9.8 x (2 x 4. 2) = 823. 2J b. How much work has gravity done during this exercise? W = F . S If F and S are in same direction then W is positive If F and S are in opposite direction then W is negative In this case, the force and distance are in the opposite direction. W =- mgh =- 10 x 9.8 x (2 x 4. 2) =- 823. 2JC. At the top of the two ights of stairs you put the 10 kg block on a ramp that makes a 60 degree angle with the horizontal and is two stories high, with the bottom at the same height as the floor. {see diagram below.) Draw a free body diagram of the block on the ramp. If the coefcient of friction between the block and the slide is us 2 0. 4, will the MM block slide down the ramp? Justify your answer. F .. :0.4X10> Ffrictim So the block will slide down the ramp If the block slides, how much work does friction do during the slide? How much work does gravity do? Work done by friction Since the force and distance are in the opposite direction, the work is negative. W : mgh : 10 X 9.8 X (2 X 4. 2) : 823. 2] friction Work done by gravity Since the force and distance are in the same direction, the work is positive. w =mgh=10>