5. Suppose a block is drag straight forward on a flat surface. The block
has
moved 20 m by applying 500 N force.
Calculate the work done by the force
against friction

Work = force x distance
= 500 x 20
= 10,000 J

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.

The upward force acting on the wing of a airplane in flight is known as the "lift" force. (d)