Question

A 145 kg baseball is thrown so that it acquires a speed of 25m/s. what is its kinetic energy

Answer 1

kinectic energy = 1/2mv^2

mass = 145kg

velocity = 25m/s

kinectic energy = 1/2 * 145 * 25

kinectic energy = 1812.5 Joules(J)

Answer 2

Answer:

The work done by the thrower on the ball to throw it with a speed of $25 \mathrm{~m} / \mathrm{s}$is equal to $45.3125 \mathrm{~J}$

Explanation:

• A$145 \mathrm{~g}$ baseball is thrown with a speed of $25 \mathrm{~m} / \mathrm{s}$.
• When the thrower picks up the ball it is at rest.
• When it leaves the hand of the person that is throwing the ball it has a speed of $25 \mathrm{~m} / \mathrm{s}$.
• An object with a mass $\mathrm{m}$ and moving with a velocity $v$ has kinetic energy given by $K.E. =(1 / 2)^{*} \mathrm{~m}^{*} v^{2}$
• Initially the ball is at rest and has kinetic energy equal o 0 .
• When it leaves the thrower's hand it has a speed of $25 \mathrm{~m} / \mathrm{s}$. Its kinetic energy when moving at $25 \mathrm{~m} / \mathrm{s}$ is equal to $(1 / 2)^{*} 0.145^{*} 25^{2} =45.3125 \mathrm{~J}$ This addition in energy is the work done by the thrower on the ball.
• The work done by the thrower on the ball to throw it with a speed of $25 \mathrm{~m} / \mathrm{s}$is equal to $45.3125 \mathrm{~J}$