Mechanics: Momentum and Collisions

Momentum and Collisions: Audio Guided Solution

Problem 6:

An interesting story is often told of baseball star Johnny Bench when he was a rookie catcher in 1968. During a Spring Training game, he kept signaling to star pitcher Jim Maloney to throw a curve ball. Maloney continuously shook off Bench's signal, opting to throw fastballs instead. The rookie catcher walked to the mound and told the veteran Maloney that his fastball wasn't fast enough and that he should throw some curve balls. Bench again signaled for a curve. Maloney shook of the signal and threw a fastball. Before the ball reached the plate, Bench took off his glove; he then caught the pitch barehanded.

a. Determine the impulse required to stop a 0.145-kg baseball moving at 35.7 m/s (80.0 mi/hr).
b. If this impulse is delivered to the ball in 0.020 seconds, then what is magnitude of the force acting between the bare hand and the ball?

Audio Guided Solution

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Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., m = 1.50 kg, vi = 2.68 m/s,  F = 4.98 N, t = 0.133 s, vf = ???.
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.

Get more information on the topic of Momentum and Collisions at The Physics Classroom Tutorial.