# Help with static equilibrium

1. Jan 30, 2005

### ramin86

6. [PSE6 12.P.022.] Stephen is pushing his sister Joyce in a wheelbarrow when it is stopped by a brick 7.83 cm high (Fig. P12.22). The handles make an angle of 15.0° below the horizontal. A downward force of 389 N is exerted on the wheel, which has a radius of 20.3 cm.

There was a similar problem in the book, so I used the formulas that they had in there.

(a) What force must Stephen apply along the handles in order to just start the wheel over the brick?
N
For this one, I did F= mg * sqrt(2rh-h^2)/(2r-h), with mg = 389N, and the radius of .203m, and a height of .0783m, and I came up with 190N, however, the answer turned out wrong.

(b) What is the force (magnitude and direction) that the brick exerts on the wheel just as the wheel begins to lift over the brick? Assume in both parts that the brick remains fixed and does not slide along the ground.
Magnitude
kN
For this, I did R = sqrt((mg)^2) + F^2), again turned out wrong

(c)Direction
And for this, I used tan = mg/f and solved for theta, however, it turned out wrong as well.
° above the horizontal (to the left)