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21. If the pendulum is released from rest, the maximum speed the bob attains is most nearly (A) 1 m/s (B) V2m/s (C) 2 m/s (D) 4m/s (E) 6 m/s 22. Some students want to calculate the work done by friction as an object with unknown mass moves along a straight line on a rough horizontal surface. The students have a force probe, a meterstick, and a stopwatch. Which of the following will allow the students to take the measurements needed to calculate the work done by friction? (A) Pulling the block at an unknown constant acceleration with the force probe for a measured time (B) Pulling the block at an unknown constant speed with the force probe for a measured time (C) Pulling the block at an unknown constant acceleration with the force probe for a measured distance (D) Pulling the block at an unknown constant speed with the force probe for a measured distance AP Physics 1 Page 13 of 25 AP CollegeBoard Test Booklet Energy Practice 2022 23. 14 / 25 A block is set on a rough horizontal table where frictional forces are not negligible. The block is pushed against a horizontal spring, and it is released at time t = 0. The spring pushes the block across the table. At time t = t1, the block leaves the table. The block strikes the ground at time t = t2. Which of the following describes the change in mechanical energy of the block-spring system for times 0