Question

Josie ran at an average speed of 16 m/s. if her mass 10 kg, what was her kinetic energy as she crosses her finish line?

Answer 1

I have to be honest with you . . . It's not possible to determine the answer with only the information given in the question.

Kinetic energy = (1/2) (mass) (speed squared).

Josie's Kinetic energy as she crosses the finish line is

(1/2) (her mass) (her speed as she crosses the finish line)².

That's (5 kg) x (her speed as she crosses the finish line)² .

But read the question again.

WE DON'T know her speed as she crosses the finish line.

The question only tells us her average speed for the whole race.

We can be confident that her Average Kinetic Energy was

(5 kg) (16 m/s)²  =  1,280 Joules.

But we can't tell what her kinetic energy was as she crossed the finish line, beause we don't know what her speed was at that instant.

Answer 2

Answer: 1280 J

$KE=\frac{1}{2}mv^{2} \\\\KE= \frac{1}{2} (10 kg)(16 m/s)^2\\=1280 J$