So there are different ways this could be solved. I'll do try to explain it the way I was taught...
Simon is riding his bike at 12 km/hr relative to the sidewalk, away from where Keesha is.
Simon throws the ball at Keesha, at 5 km/hr.
Keesha sees the ball approaching her at (12-5) = 7 km/hr relative to the ground to her.
Therefore the answer is: 7 km/hr
Earth's HYDROLOGIC cycle moves water from one reservoir to another.
Answer: a) 127 eV; b) there is no change of kinetic energy.
Explanation: In order to explain this problem we have to use the change of potentail energy ( conservative field) is equal to changes in kinetic energy. So for the proton ther move to lower potential then they gain kinetic energy from the electric field. This means the electric force do work in this trayectory and then the protons increased changes its speed.
If we replace the proton by a electron we have a very different situaction, the electrons are located in a lower potental then they can not move to higher potential if any external force does work on the system.
In resumem, the electrons do not move from a point with V=87 to other point with V=-40 V. The electric force point to high potential so the electrons can not move to lower potential region (V=-40V).
At -40.
-40 gives the same reading for Fahrenheit and Celsius scale.
im not gonna write a research paper but this is the really easy way write global warming talk about animals the polar ice caps and water levels then for what causes it burning fossil fuels and energy plants. then finish off with its awful and we should use solar or geothermic or wind or when the time comes fusion not fission fusion makes helium from hydrogen then burylliam from helium then oxygen and silicon so on so forth instead of fissions uranium,plutonium and thorium and with radioactive waste