2-Questions a.If a piston-cylinder expands slowly and smoothly while being expos

Question

2-Questions

a.If a piston-cylinder expands slowly and smoothly while being exposed to a constant external pressure, then the expansion must occur at constant internal pressure. Explain why.

b.In making the batter for a cake, I use a mixer to blend the ingredients. Electric energy was used to spin the beaters, so where did that energy go?

c.You have a big professional presentation and so you need to iron your clothes. You plug the iron into the wall, let it heat up, iron your clothes, then turn off the iron and leave it out until it cools down. Explain what types of energy are changing throughout this process, and explain how energy is transferred into and out of the iron during this process.

d.You pick a baseball up off the ground and then throw it into the air and let it fall back to the ground. It bounces a few times and rolls for a bit before coming to rest. Explain what types of energy the ball has at each stage throughout this process, and explain how energy is transferred into and out of the ball during this process.

e. 2.22 [68 kW]

f. 2.28 [-12kJ, -7.3 kJ, -6.4 kJ]

Explanation / Answer

a) If a piston-cylinder expands slowly and smoothly while being exposed to a constant external pressure, then the expansion must occur at constant internal pressure because if the pressure difference between the inside and outside of the piston is more then the piston suddenly moves forward or backward based on the values. If the pressure inside the piston is slightly more(just a small value) than the outside then the piston moves slowly and smoothly, the pressure difference is almost negligible. Its similar to quisistatic process.

b) The electrical energy is converted to mechanical energy in rotating/spinning the beaters. The mechanical energy is then converted to break the batter (eggs, flour, sugar,etc) into smaller molecules and mix properly.

c) The electricity passes to the iron box and heats up the base of the iron box. Conversion is from Electrical energy to heat energy. The heat from the iron box passes on to clothes while ironing and the cloth gets tidy and neat. Once ironing is done. The electrical energy supply is stopped. But the heat dissipation from the iron box to the environment happens through the conection heat transfer. The iron box cools down till its temperature reaches that of the atmospheric temperature.

d) Once the ball is picked up it possesses potential energy gue to its height. As the ball is thrown its kinetic energy keeps on decreasing and the potential energy increases. At the highest level achieved the potential energy is maximum and the K.E is zero. As the ball drops down the kinetic energy increases and P.E decreases. On collision with ground, some energy is lost and it continues till it loses all the energy and finally rolls and stops.

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