Gravity if you are coasting.
Gravity pulls it down and the weight of a car is less dense than a hill and therefore it goes down
a hill is a steep road that has either grass or something else and goes both up and down
My ball rolled down the hill.
Light
a penguin rolling down a hill
It goes down hill from left to right.
Man The young go up the hill walking on two legs, The old come down the hill using a cane.
gravity is the one to blame . gravity pulls down the biker closer to earth so it goes faster going down and slower going down
If you are driving a loaded tractor trailer, you would downshift to gain more power when going up hill and downshift to control speed when going down hill.
potential energy
a wheel barrow
skiing is......... going down hill on snow using skies to guid you