Lulu wants to swing a 0.10-kg Twinkie tied to one end of a cord in a horizontal circle of radius 0.50 m with a tangential speed of 0.20 m/s. What centripetal force must she exert on the mass through the cord?

26.4 is about the right time

The answer should be a.

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.