It is 10.20 m from the ground.
<u>Explanation:</u>
<u>Given:</u>
m = 0.5 kg
PE = 50 J
We know that the Potential energy is calculated by the formula:

where m is the is mass in kg; g is acceleration due to gravity which is 9.8 m/s and h is height in meters.
PE is the Potential Energy.
Potential Energy is the amount of energy stored when an object is stationary.
Here, if we substitute the values in the formula, we get

50 = 0.5 × 9.8 × h
50 = 4.9 × h

h = 10.20 m
Calculating acceleration involves dividing velocity by time — or in terms of units, dividing meters per second [m/s] by second [s]. Dividing distance by time twice is the same as dividing distance by the square of time. Thus the SI unit of acceleration is the meter per second squared.
This I what it showed when I looked it up so if your writing this down try and put some in your own words
To stop the car it would be 100m because if the car is going to 65km/h then it would still be 100km/h
I do not know what the school expects as an answer, but advantage of reflecting telescopes is that there is only one major reflecting surface, so it is quite easy to create a 6 or 8 inch telescope by an amateur, after adding on a prism and an eyepiece. (a microscope eyepiece could be used).
MY answer would be "easier to build". (it still takes tens of hours to grind and polish the single plane surface to a parabolic surface).
Electromagnetic waves all have the same velocity in the same medium. However, since frequencies vary widely, so do wavelengths.