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Brut [27]
3 years ago
13

A student does 25 J of work on the handle of a pencil sharpener. If the pencil sharpener does 20 J of work on the pencil, what i

s the efficiency of the sharpener?
Physics
1 answer:
allsm [11]3 years ago
3 0

Answer:

80%

Explanation:

Efficiency of machine = work output/work input  ×100 %

From question, work output = 20J

Work input = 25J.

Therefore efficiency = 20/25 × 100 %

Efficiency = 20×4 %

Efficiency = 80%

I hope this was helpful, please mark as brainliest

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The speed of a boat in still water is 20 mph. it travels from one pier to another with the current in 4 hours and back against t
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3 0
3 years ago
A pipe open at both ends has a fundamental frequency of 220 Hz when the temperature is 0°C. (a) What is the length of the pipe?
Allushta [10]

Explanation:

It is given that,

Fundamental frequency, f = 220 Hz

(a) We know that at 0 degrees, the speed of sound in air is 331 m/s.

For open pipe, \lambda=2l

l is the length of pipe

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v=f\lambda

l=\dfrac{v}{2f}=\dfrac{331}{2\times 220}=0.75\ m

(b) Let f' is the fundamental frequency of the pipe at 30 degrees and v' is its speed.

v'=331\sqrt{1+\dfrac{T}{273}}

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