B is the answer! Because no one would be pushing the rock all the way down the hill it would just go down by itself by rolling!!
Hope i helped plz mark as brainlist and 5 star'!
Kinetic energy = (1/2) (mass) x (speed)²
At 7.5 m/s, the object's KE is (1/2) (7.5) (7.5)² = 210.9375 joules
At 11.5 m/s, the object's KE is (1/2) (7.5) (11.5)² = 495.9375 joules
The additional energy needed to speed the object up from 7.5 m/s
to 11.5 m/s is (495.9375 - 210.9375) = <em>285 joules</em>.
That energy has to come from somewhere. Without friction, that's exactly
the amount of work that must be done to the object in order to raise its
speed by that much.
The ideal mechanical advantage (IMA) can be determined by the following equation:
IMA= Input distance/Output distance
The Input distance and Output distance are:
Input distance=220 meters
Output distance=110 meters
When you substitute in the equation of the ideal mechanical advantage (IMA), you obtain:
IMA= Input distance/Output distance
IMA= 220 meters/110 meters
IMA=2