Work=f.d
Work=100*50 = 500
Power = work/time = 500/4
=125 watt
<u>Answer</u>:
The stream flowing at a speed of 
<u>Explanation</u>:
Given:
Distance = 2km (both in upstream and downstream)
The speed in still water be x km/hr.
The speed in upstream = 4-x
Speed in downstream = 4+x
Solution:
We know that, Speed = distance/time
So, Time = distance/speed
Therefore,




By cancelling 2 on both sides,




Result:
Thus the speed of the stream is 
The answer is 2) 1.0c. Light will always propagate through a vacuum at the speed of light “c”; even when moving at a significant fraction of the speed of light, observers will still measure this as the speed of light and the difference is resultant of time dilation.
Answer:
3.53*10^{-7} m
Explanation:
Photon that can rupture the bonds are those with the energy of the bond dissociation energy. If we want to know the energy for each molecule we have to take into account that:

Hence, we have

but the energy is also:

where h is the Planck's constant and c is the speed of ligth. By replacing we obtain:

hope this helps!
Answer:
a) three times greater
Explanation:
Remember the heat capacity is the necessary heat to increase the temperature 1 ºC to an specific mass of the substance, in this case since the water and the metal have the same mass, is easier to compare just the neccesary heat.
Since water increases 20 ºC and the metal 60 ºC, it was neccesary 3 times of the quantity of heat to the same amount of mass of the two different susbtances.
Hope it was useful