1. The problem statement, all variables and given/known data A garden cart loaded with firewood is being pushed horizontally when it encounters a step 8.0 cm high, as shown in the figure. The mass of the cart and its load is 56 kg, and the cart is balanced so that its center of mass is directly over the axle. The wheel diameter is 60 cm. 2. Relevant equations F = mg cos (theta) 3. The attempt at a solution The angle theta upon which the force is going to act when the cart goes up the slope is: (R -h) / (sqrt((R - h)2 + (h^2)) Multiplied by mg: mg * (R -h) / (sqrt((R - h)2 + (h^2)) = 56 * 9.8 * (.3-.08)/sqrt((.3-.08)^2 + .08^2) = 515.75686308 Rounded to two significant figures, this is 520. Mastering physics says the answer is 510. How come?