An elevator starts from rest with a constant upward acceleration. It moves 0.78 m in the first 0.69 s of its acceleration. A passenger in the elevator is holding a 1.8 kg box by a vertical string. What is the tension in the string while the elevator is accelerating?

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.