Explanation :
Work is done when a force is applied to create a displacement on an object.
Thus, the work done depends on the two factors i.e.
(1) Applied force (F)
(2) Distance or displacement (d)
Mathematically, work done is 
It also depends on the angle between the force and the displacement.

For example,
A person carries a weight of 20 kg and lifts it on his head 1.5 m above the surface. So, the work done by him on the luggage will be:

or


So, 
Hence, the work done by him on the luggage is 294 Joules.
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Answer: Something that's vibrating, and you also need medium for those vibrations to start in.
I hope this helped!
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- Zack Slocum
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Looks like you simply substitute the length of the femur
Well, you gave us the formula to calculate power from work and time,
but you didn't give us the formula for work. We have to know that.
Work = (force) x (distance)
The work to raise Sara to the top of the hill is
Work = (300 N) x (15 meters)
= 4,500 newton-meters = 4,500 joules .
Now we're ready to use the formula that you gave us. (Thank you.)
Power = (work) / (time)
= (4,500 joules) / (10 seconds)
450 joules/second = 450 watts.
Answer:
Explanation:
Electric field due to a point charge Q at a point at distance d is given by the relation
E = 
Since Q1 and Q2 are of the same magnitude and distance , so they will create eletric field of same magnitude. Similarly field due to rest of the charges will also be same.
The charges are situated on the corners of a square in such a way that
equal charges of Q1 and Q3 are situated on the diametrically opposite corners of the square. Fields due to these two charges will be equal and opposite in direction. Therefore net field due to these two charges will be zero.
On the same ground, we can say that field due to Q2 and Q4 at the centre will be equal and opposite and therefore they will cancel out each other. Net field at the centre will be zero
Overall, net field due to all the four charges will be zero