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