1. The problem statement, all variables and given/known data A civil engineer wishes to redesign the curved roadway in Interactive Example 5.7 in such a way that a car will not have to rely on friction to round the curve without skidding. In other words, a car moving at the desig- nated speed can negotiate the curve even when the road is covered with ice. Such a curve is usually banked, meaning that the roadway is tilted toward the inside of the curve. Suppose the designated speed for the curve is to be 13.4 m/s (30.0 mi/h) and the radius of the curve is 35.0 m. At what angle should the curve be banked? 2. Relevant equations nsin(theta) = mv2 /r ncos(theta) = mg tan(theta) = v2/rg 3. The attempt at a solution I had thought that looking at horizontal movement on the slope you would use mgsin(theta) = mv2/r, so that the force is parallel with the slope. Why are we not doing this? Thanks.