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Section 9.4 Using Impulse
Activity 9.4.1 . The Ball and the Ground.
You drop a
\(0.05 \mathrm{~kg}\) tennis ball from rest and it takes
\(0.5 \mathrm{~s}\) to hit the ground.
(a) Use the Impulse-Momentum theorem to find the velocity of the ball just before impact with the ground.
(b) The tennis ball rebounds from the ground with the same speed as impact. The collision takes
\(0.01 \mathrm{~s}\text{.}\) Find the average net force on the tennis ball.
Activity 9.4.2 . The Pitcher.
A baseball pitcher throws a baseball toward home plate. The mass of the baseball is about
\(145 \mathrm{~g}\text{.}\) It takes approximately
\(0.2 \mathrm{~s}\) for the pitcher to speed up the ball.
(a) Estimate the speed of the ball (in m/s) as it leaves the pitcher’s hand.
(b) Sketch a free-body diagram for the pitcher and the baseball.
(c) Is momentum conserved for the baseball? For the pitcher? For the system of both the baseball and the pitcher?
(d) Estimate the magnitude of the force the pitcher acts on the ball.
(e) Estimate the magnitude of any other forces acting on the pitcher.
