Question

What is the mass of a baseball if the kinetic energy is 140 J when the baseball is thrown at 96 mph? 0.021 g A batter hits a pop fly, and the baseball reaches an altitude of 270 ft. If we assume that the ball was 3 ft. above home plate when hit by the batter, what is the ball's increase in potential energy? J

Answer 1

Explanation:

It is given that,

Kinetic energy of the baseball, E = 140 J

Speed with which the baseball is thrown, v = 96 mph = 42.91 m/s

(a) The kinetic energy of the ball is given by the formula as :

$E=\dfrac{1}{2}mv^2$

$m=\dfrac{2E}{v^2}$

$m=\dfrac{2\times 140}{(42.91)^2}$

m = 0.15 kg

(b) The ball reaches a height, h = 270 ft = 82.29 m

The assumed height of the ball, h' = 3 ft = 0.914 m

The increase in potential energy of the ball is :

$\Delta PE=mg(h-h')$

$\Delta PE=0.15\times 9.8\times (82.29-0.914)$

$\Delta PE=119.62\ J$

So, the increase in potential energy of the ball is 119.62 Joules. Hence, this is the required solution.