Free Response Question#2: Some of these components of this question were marked wrong or marked half-wrong on a test. I need the correct answers and explanations for test corrections.

(Green color ink - Teacher's grading and comments)

2. This question is a long free-response question. Show your work for each part of the question. (15 points, suggested time 20 minutes) Spring Plunger Figure 1 Do pins greater PE Block of mass m Figure 2 A spring-loaded launcher can be securely attached to a tabletop. When the spring is at its uncompressed length, the plunger is in the position shown above in Figure 1. A small wood block can be pressed against the end of the plunger, compressing the spring a distance L as shown in Figure 2. When the block is released, the plunger pushes the block along the tabletop. Two pins are attached to the edge of the table to prevent the plunger from extending beyond the table. When the plunger hits the pins, the block then leaves the table. There is nonnegligible friction between the block and the tabletop (s is slightly less than L) (s is significantly Table 1 IS = A; less than L) S = B Table 2 greater distance less Taller Table Shorter Table The launcher can be moved closer to or farther from the edge of the tabletop. Students set up tables 1 and 2, as shown above, with tabletops that are made of the same material. On table 1, which is taller than table 2, the launcher is positioned so that the distance s=A between the launcher and the edge of the tabletop is slightly less than L. On table 2, the launcher is positioned so that the distance s=B between the launcher and the edge of the tabletop is significantly less than L. On both tables, the block is released from rest and loses contact with the plunger at the moment the plunger reaches the pins. K is the spring stiffness constant m is the mass of the block L is the distance the spring is compressed. Scantron M-882-E-5:41 u (mu) is the coefficient of kinetic friction between the block and the tabletop s the distance between the launcher and the edge of the tabletop.W = FX Ax GOOD Assume the spring is ideal, the plunger has negligible mass, the block loses contact with the plunger immediately after it reaches the end of the table, and there is non-negligible friction between the tabletops and the blocks. a) Without manipulating equations, explain why the block launched from table 2 could have a greater speed when it leaves the table than the block launched from table 1 does. $/3 - Table 2 will be launched at a greater speed because the displacement is shorter than takel I, causing the plunger to immediately, hit the blocks with a shorter amount of time. ( leading to more power) (b) Does the block launched from table 2 spend more, less, or the same amount of time in the air than the block launched from table 1 does? Explain your reasoning. 13 - They stay the savce time in the air since they are both acted on by gravity ! But table 2 is shorter. (c) Consider the system consisting of only the block. Determine the change, if any, in the total mechanical energy of the system from the instant the block leaves the table to the instant immediately before it reaches the ground. of from the spring to the ramp, the ME is relatively the same, but as the block forthurs the ground the ME decreases since the HE decreases. No height can't say/use potential to multiply The students correctly derive an equation for the speed v of the block when it is at the edge of the tabletop, in terms of s (the distance between the launcher and the edge of the tabletop): FF = M - N (2Ls - $2) - 2ugs. (d) Does this equation for v support your argument from part (a) that the block launched from table 2 could have a larger speed when it leaves the table than the block on table I does? Briefly explain why or why not. (a) yes, it is possible since the xbetween the plunger and the blocks is shorter than table!. FF = M - N As"s' increases v decreases. (e) The students now repeat the scenario with identical setups except that the coefficient of kinetic friction between the blocks and the table is larger. Does this change in the coefficient of friction make it more likely or less likely that the block launched from table 1 has a greater speed when it leaves the table than the block on table 2 does? Briefly explain your reasoning. - Ramp I has a slower speed since as the Plunger glides across the table, the friction acts on it causing it to slow down. Since there is less distance to act against the plunger on table to its speed in greater. x Less likely