[填空题]
What minimum horsepower must a motor hs+ /wrtc;d-nsmqo ,e 4ave to be nyk c kua51ob,alsi n -sn;:m-g f,s;8able to drag a 310-kg box along a level floor at a speed of 1.2m/s if the coeffikm5s:f os nn-bgsa;,1yu c;a ,-nlk8icient of friction is 0.45? hp
