A 1.9 kg otter starts from rest at the top of a

muddy incline 90 cm long and slides down to
the bottom in 0.50 s.
What net external force acts on the otter
along the incline?
How do I do this?

1 answer

d = 0.5at^2 = 0.90m,
0.5a(0.5)^2 = 0.90,
0.125a = 0.90,
a = 0.90 / 0.125 = 7.2m/s^2.

F = ma = 1.9 * 7.2 = 13.7N.