[填空题]
A city planner is working:0nfo9m(hgn:jb; nu r: b4s do o c pn1q cq/r-mo/9dgmb0i 7pv:n the redesign of a hilly portion of a city. An important consideration is how steep the roads can be so that even low-powered cars can get up the hills without slowing down. A particvdcp/-9 c: m 0n71gmqqo/pbi rular small car, with a mass of 1100 kg , can accelerate on a level road from rest to 21$ \mathrm{~m} / \mathrm{s}(75 \mathrm{~km} / \mathrm{h})$ in 14.0 s . Using these data, calculate the maximum steepness of a hill. $^{\circ}$
