Describe a device that transforms thermal energy into another useful form

Trumpeter a holds a b-flat note on the trumpet for a long time. person c is running towards the trumpeter at a constant velocity. person b is running away from the trumpeter at the same rate. person d is standing still the whole time. which person hears a frequency that is lower than the b-flat?

What occurs during a combustion reaction

How much energy must a refrigerator absorb from 225 g of water so that the temperature of the water will drop from 35°c to 5°c