How do i find the Net external force?? PLEASE HELP!!?

Question

A 2.0 kg otter starts from the rest at the top of a muddy incline 85 cm long and slides down to the bottom in 0.50 seconds. What net external force acts on the otter along the inline?? How do find the answer??

PLEASE HELP!!!!! THANKS IN ADVANCE TO THOSE WHO DO!!!

Answer 1

Use conservation of mechanical energy.

The initial energy is gravitational potential energy, mgh. Alas, you don't know h. If you had the angle of the incline, it would be ( 85 cm ) ( sin of that angle ).

The final energy is kinetic, 1/2 m v^2.

The average velocity is 85 cm in .5 seconds. This is equal to ( v + vo ) / 2, the average of the final and initial velocities. The initial velocity is zero; the final velocity is what you're looking for.

You will probably find that there is less kinetic energy at the bottom than there was potential energy at the top. The lost energy is due to the work done by friction. This work is equal to the force of friction multiplied by the distance ( 85 cm ).