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QuizMultiple Choice

Kinetic Energy — Quiz

Question 1 • Physics

Which best describes Lenny’s error?

Answer
A
In Step 1, he should have found the square root of 400 cap j instead of squaring 8 meters per second .
B
In Step 1, he should have multiplied 8 meters per second by 2 instead of squaring it.
C
In Step 2, he should have divided 64 the fraction with numerator m squared and denominator s squared by 400 cap j instead of dividing 400 cap j by 64 the fraction with numerator m squared and denominator s squared .
D
In Step 3, he should have multiplied 6 point 2 5 cap j per the fraction with numerator m squared and denominator s squared by 2 instead of dividing it by 2 .

Explanation

Using the kinetic energy formula, 400 J = ½mv². Squaring 8 m/s gives 64 m²/s², and dividing 400 J by that gives 6.25 kg. To solve for the mass, you must multiply 6.25 kg by 2, not divide by 2, so the error is in Step 3.

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