Explanation:
The machine whose efficiency is 100% is known as perfect machine .This machine is not possible in real life because every machine is affected by the overcoming friction due to which is efficiency become less than hundred percent .
From the above reaction the temperature of the surroundings will increase.
The Archimedes principle is a principle that is expressed as a law that states that a body immersed in a fluid, whether fully or partially, is subject to an upward force of the same magnitude as the weight of the fluid it displaces.
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Answer: 0.25 m/s
Explanation: Speed = wavelengt · frequency
v = λf and frequency is 1/period f = 1/T
Then v = λ/T = 5 m / 20 s = 0.25 m/s
A) it is always changing direction