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Physics/work and energy


1.the potential energy of a freely falling object decreases progressively.does this violate the law of conservation of energy?why?
2.a freely falling object eventually stops on reaching the ground.what happens to its kinetic energy on reaching the ground?
3.what kind of energy transformation takes place when a body falls from a certain height?explain.
4.what kind of energy transformation takes place when a body is thrown upward?explain.
5.give the basic design of a simple pendulum and explain the conservation of mechanical energy.

1. No, because the law of energy conservation allows for the conversion of one type of energy into another type of energy as long as the total energy remains constant. in this case the potential energy ofthe following objectis converting into an equal amount of kinetic energy.
2. When the object strikes the ground it's energy is converted into work by deforming the schoe of the ground, by deforming the shape of the object, by generating heat in both the object and the ground and by releasing energy in the form of sound. The total of all of these will still equal the total kinetic energy of the object just as it reaches the ground.
3. Gravitational energy converts to Kinetic Energy then converts into Work and Heat.
4. When an object is thrown upward Work is done to the object giving the object Kinetic energy. As the object rises this Kinetic Energy converts into Gravitational Potential Energy and finally back into Kinetic Energy as is falls back to the ground where the Kinetic Energy is then converted into Work and Heat.
5. A simple pendulum consists of a mass, called the "bob" suspended from the end of a string whose mass is typically unimportant compared to the mass of the bob. Work is then done of this mass pulling it back and giving the mass Gravitational Pontenial Energy. The mass is then released and th Gravitational Potential Energy is then converted into Kinetic Energy as the mass reaches the lowest point. The mass then continues on to the other side where it's Kinetic Energy converts back into Gravitational Potential Energy where the cycle then repeats: GPE to KE to GPE to KE etc. Energy is being converted. All this assumes that the effect of air friction on the pendulum is insignificant.


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James J. Kovalcin


I am teaching or have taught AP physics B and C [calculus based mechanics & electricity and magnetism] as well as Lab Physics for college bound students. I have a BS in Physics from the University of Pittsburgh and a Master of Arts in Teaching from same. I have been teaching physics for 34 years. I am constantly updating my skills and have a particular interest in modern physics topics.

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