A roller coaster car is released from a standing start at the top of a 20.0-m hill. The car rolls down the hill to a point 10.0 m above the ground, then up a second hill to 15.0 m, and then down again to point X at 8.00 m above the ground. Use what you know about the sum of the kinetic and potential energies to find the car's speed at X. A.
11.7 m/s
B.
12.5 m/s
C.
15.3 m/s
D.
19.8 m/s

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.