The proper time would be the time measured in the rest frame of the event, so in this case the observer on mars would measure the proper time.
Answer:
Zero because the applied force is perpendicular to the motion of the object.
No work is done on an object moving is a circular path about a central attractive force.
Any work done in such a case would result in a change in the orbit.
You need the picture. However, since I'm doing PLATO as well, here's the answer:
The third position in which the cyclist is going downhill is the position where the cyclist has the maximum kinetic energy. The other two photos show that the biker has more potential energy.
Thanks, let me know if this helped!
Volumetric cylinders and volumetric flasks
