The point of this question is to compare rest energy and kinetic energy at low s

Question

The point of this question is to compare rest energy and kinetic energy at low speeds.

A baseball is moving at a speed of 34 m/s. Its mass is 145 grams (0.145 kg).

(a) What is its rest energy? _____J
(b) Is it okay to calculate its kinetic energy using the formula

mv2?Yes, because the formula

mv2 for kinetic energy is always correct.

No, because you always have to use the formula ?mc2 ? mc2.

    Yes, because

v << c.

(c) What is its kinetic energy? ____J
(d) Which is true?

The kinetic energy is much bigger than the rest energy.The kinetic energy is approximately equal to the rest energy.    The kinetic energy is much smaller than the rest energy.

Explanation / Answer

A)

Here , u = 34 m/s

m = 0.145 Kg

a)

rest energy = mc^2

rest energy = 0.145 * (3*10^8)^2

rest energy = 1.305 *10^16 J

the rest energy is 1.305 *10^16 J

b)

Here , as v << C

Kinetic energy = 0.5 mv^2

c)

KE = 0.5 mv^2

KE = 0.5 * 0.145 * 34^2

KE = 83.8 J

the kinetic energy of baseball is 83.8 J

d)

TRUE statement is

The kinetic energy is much smaller than the rest energy.

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