As it slides down the hill, gravity exerts a forward (downhill) force on the toboggan and it moves forward (downhill).
(it; slides; down the hill) (gravity; exerts downhill; force on the toboggan; T:As it slides down the hill) (it; moves; forward; downhill)
it gravity it
slides exerts downhill moves
down the hill
force on the toboggan T:As it slides down the hill
forward downhill