1. A possible force vs. time curve for a ball struck by a bat is shown in the figure.
(a) Calculate the impulse delivered to the ball.
(b) This 0.25 kg ball was initially moving toward the bat at a speed of 20 m/s. Calculate the exit speed of the ball.
Understandable mistake, combo platter: The student who used the max force rather than the average force to calculate impulse, AND who didn't account for the ball's changing direction, got something like 68 m/s. Well, that's about 150 mph, and still not horrid -- after all, that's only 40% above the typical 100-120 mph exit speeds in the majors. (I'm recalling my Physics of Baseball by Robert Adair; I hope I have that value right. Please correct me in the comments if I'm wrong.) That answer loses only the two points for the direction change issue.