A baseball with a mass of 0.75 kg is traveling at a speed of 35 m/s. Its is caught in the catchers mitt and brought to a stop.

Question

A. What is the change in the momentum of the ball?

B. If it takes the catcher 1.5 seconds to stop the ball, how much force does the glove apply to the ball?

Answer 1

Consider this problem with a more realistic mass for the baseball, which would be 146.5 grams or 0.1465 kilograms.

With Momentum equal to (Mass Times Velocity), the moving baseball would strike the glove with

Momentum of (0.1465 × 35) kilograms-dot-meters-per-second or 5.1275 kg•m/s. The baseball

would drive the glove back until the glove brakes the baseball to zero velocity. Then the baseball's

change in momentum would be (0.1465 × 0) kg•m/s minus (0.1465 × 35) kg•m/s or -5.1275 kg•m/s.

The baseball is driving the glove backward for 1.5 seconds with decreasing momentum until it has zero velocity (and momentum). At the instant that the baseball hits the glove, its unretarded momentum is 5.1275 kg•m/s. Dividing

5.1275 kilograms-dot-meters-per-second by 1.5 seconds will give the force applied by the glove to the ball as (5.1275/1.5) kg•m/s ÷ s.

Rewrite (5.1275/1.5) kg•m/s ÷ s as 3.418333333333 kg•m/s² equivalent to

3.42 Newtons. Writing the final answer as -3.42 Newtons indicates that the glove forces the baseball opposite the baseball's direction of travel.