19. An object that is thrown straight up falls back to Earth. This is one-dimensional motion. (a) When is its velocity zero? (1)} Does its velocity,r change direction? to} Does the acceleration have the same Sign on the way up as on the way down? 30. A woodchuck runs 20 m to the right in 5 s, then turns and runs 10 m to the left in 3 s. (a) What is the average velocity of the woodchuck? (b) What is its average speed?28. A cyclist rides 8.0 km east for 20 minutes, then he turns and heads west for 8 minutes and 3.2 km. Finally, he rides east for 16 km, which takes 40 minutes. (a) What is the nal displacement of the cyclist? (b) What is his average velocity? 35. A particle moves along the x-axis according to x(!) = 10/ - 21- m. (a) What is the instantaneous velocity at t = 2 s and t = 3 s? (b) What is the instantaneous speed at these times?46. (3) Sketch a graph of velocity versus time corresponding to the graph of displacement versus time given in the following gure. {h} Identify the time or times (ta, 11,, It, etc.) at which the instantaneous velocity has the greatest positive value. (:2) At which times is it zero? (d) At which times is it negative? Position 1: Time I 66. Calculate the displacement and velocity at times of(a) 0.500 s. (b) 1.00 s, [c}1.50 s, and (cl) 2.00 s for a ball thrown straight up with an initial velocity of 15.0 mfg. Take the point of release to be m = 0. 94. A 10.0m1ong truck moving with a constant velocity ' of 97.0 kmfh passes a 3.0-m-long car moving with a constant velocity,r of 30.0 mm. How much time elapses between the moment the front of the truck is even with the hack of the ear and the moment the ' back of the truck is even with the front of the car? 102. A coin is dropped from a hot-air balloon that is 300 m above the ground and rising at 10.0 m/s upward. For the coin, find (a) the maximum height reached, (b) its position and velocity 4.00 s after being released, and (c) the time before it hits the ground.113. The position of a particle moving along the X-axis varies Twith time according to xi!) = 5.0!2 4.0?3 In. Find (a) the velocity and acceleration of the particle as functions of time, (b) the velocity and acceleration at t= 2.0 s, {c} the time at which the position is a maximum, (cl) the time at which the velocity is zero, and (e) the maximum position. 114. A cyclist sprints at the end of a race to clinch a victory. She has an initial velocity of 11.5 m/s and accelerates at a rate of 0.500 m/s for 7.00 s. (a) What is her final velocity? (b) The cyclist continues at this velocity to the finish line. If she is 300 m from the finish line when she starts to accelerate, how much time did she save? (c) The second-place winner was 5.00 m ahead when the winner started to accelerate, but he was unable to accelerate, and traveled at 11.8 m/s until the finish line. What was the difference in finish time in seconds between the winner and runner-up? How far back was the runner-up when the winner crossed the finish line