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3 years ago

If the work put into a lever is 930 joules and the work accomplished is 870 joules, the efficiency of the lever is _____.

2 answers:

5 0

♥ C) 94%
♥ If the work put into a lever is 930 joules and the work accomplished is 870 joules, the efficiency of the lever is 94%.
♥ <span>870/930=93.5
</span>♥ And rounded you get 94.

Dmitriy789 [7]3 years ago

4 0

The correct answer to this question is C) 94%.

CALCULATION:

As per the question, the work put into a lever is 930 Joule.

Hence, input work W = 930 Joule.

Work accomplished by the lever is 870 Joule.

Hence, the output work W' = 870 Joule.

We are asked to calculate the efficiency of the level.

The efficiency of the lever is defined as the ratio of output work to the input work.

Mathematically efficiency $\eta=\ \frac{W'}{W}$

$=\ \frac{870\ J}{930\ J}$

$=\ 0.935$

In percentage, efficiency $=\ 0.935\times 100$

$=\ 93,5\%$

$=\ 94\%$ [ans]

Hence, the efficiency of the lever is 94%.

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Answer:

Mass of bullet is m=0.01kg

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3 years ago

Need help solving this question.

MatroZZZ [7]

Answer:

See the answers below.

Explanation:

to solve this problem we must make a free body diagram, with the forces acting on the metal rod.

The center of gravity of the rod is concentrated in half the distance, that is, from the end of the bar to the center there is 40 [cm]. This can be seen in the attached free body diagram.

We have only two equilibrium equations, a summation of forces on the Y-axis equal to zero, and a summation of moments on any point equal to zero.

For the summation of forces we will take the forces upwards as positive and the negative forces downwards.

ΣF = 0

$-15+T-W=0\\T-W=15$

Now we perform a sum of moments equal to zero around the point of attachment of the string with the metal bar. Let's take as a positive the moment of the force that rotates the metal bar counterclockwise.

ii) In the free body diagram we can see that the force acts at 18 [cm] of the string.

ΣM = 0

$(15*9) - (18*W) = 0\\135 = 18*W\\W = 7.5 [N]$