- #1

noleguy33

- 26

- 0

## Homework Statement

The first part is a donkey is pulling a cart with zero acceleration and I've found the coefficient of kinetic friction in the bearings and the wheel, and the coefficient of static friction of the donkey in the ground. Part two I'm having problems with-

This time, a the donkey is pulling hard (almost starting to slip) on the same cart. The cart and donkey are accelerating at 0.24[m/s2] to the left without slippage.

Find-

a) The force by the donkey on the cart

b)The force of static friction by the surface on the donkey.

## Homework Equations

Newton's 2nd law

## The Attempt at a Solution

My first step is always to draw a FBD.

This is how I found Fd/c

Ffk - Fd/c = m(-a) /// set up that way because it's moving towards the negative x-axis

I used the same coefficient for from the first part of that problem, I got an answer of 2065[N].

I'm having an issue with the second part.

I drew a FBD for the donkey and came up with for the x-axis-

Ff(static) - Fc/d = m(-a) and I believe that gets me the right answer(or at least a common answer among classmates).

I just don't know why. Given this, the Ff(static) would be larger than Fc/d, so how exactly is the donkey moving? Thanks!

My only thought is that the Ffs is a force of the Earth on the donkey?