Ultrasound was used to check for cracks in an aeroplane wing. The ultrasound pulse would be reflected from any cracks and from the end of the wing. The diagram shows the oscilloscope trace
produced by the echo. How far along the wing was the crack? The speed of sound in metal is 5000m/s.

Acommercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35°c by rejecting waste heat to cooling water that enters the condenser at 18°c at a rate of 0.25 kg/s and leaves at 26°c. the refrigerant enters the condenser at 1.2 mpa and 50°c. if the compressor consumes 3.3 kw of power, determine (a) the mass flow rate of the refrigerant, (b) the refrigeration load, (c) the cop, and (d) the minimum power input to the compressor for the same refrigeration load.