Question

An electric drill transfers 200 J of energy into a useful kinetic energy store. It also transfers 44 J of energy by sound and 48 J of energy by heat. What is the efficiency of this drill? Round your answer to the nearest whole number.

Answer 1

The efficiency of his drill is 54 %.

Explanation:

Given that,

Out put energy = 200 J

Transfer energy by sound= 44 J

Transfer energy by heat = 48 J

We need to calculate the efficiency of his drill

Using formula of efficiency

$\eta=\dfrac{E_{out}}{E_{in}}\times100$

Put the value into the formula

$\eta=\dfrac{200-(44+48)}{200}\times100$

$\eta=54\%$

Hence, The efficiency of his drill is 54 %.

Learn more :

Topic ; efficiency

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Answer 2

Answer:

68%

Explanation:

200J of useful transfer

92J (44J + 48J) are lost as not useful energy

So add up all energy transfer (200 + 92)

Substituting into the equation  $\frac{useful,energy,transfer}{total,energy,transfer}$

This will give us 200 / 292

Which equals 0.6849315068

This needs to be put into a percentage so we times by 100

Therefore it will become 68.49315068

Then rounded to the nearest whole number it becomes 68%