Answer:
A boat travels for three hours with a... A boat travels for three hours with a current of 3 mph and then returns the same distance against the current in four hours. What is the boat's speed in still water?
Explanation:
The power expended is 500 W
Explanation:
First of all, we start by calculating the work done by the man in order to ascend: this is equal to the gravitational potential energy gained by the man, which is

where
m = 50 kg is the mass of the man
is the acceleration of gravity
is the change in height
Substituting,

Now we can calculate the power expended, which is given by

where
W = 2500 J is the work done
t = 5 s is the time elapsed
Substituting, we find

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Answer:
1.58 W
Explanation:
Since the sound spreads uniformly in all directions, it must be in a form of a circle with radius of 12 m. So the area of the circle is

From the intensity of the sound we can calculate the power at 12 m

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Answer:
High density D answers to your questions