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Energy Conversion Explanation

  1. Jul 24, 2012 #1
    Energy Conversion Explanation

    I have a ball behind suspended at the top of a ramp. The ball rolls down the ramp and triggers a switch. The switch is connected to a 9V battery and a motor and turns on once the switch is pressed. The motor acts as a fan because it has "blades" attached to it and spins and produces wind.

    I know that the ball rolling is potential to kinetic. I also believe that the battery itself is chemical potential energy that is then converted to electrical energy. When the ball hits the switch, is the act of hitting the switch considered mechanical to electrical? If someone could walk me through this with an answer it would be great.

    Thanks in advance!
  2. jcsd
  3. Jul 24, 2012 #2


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    One way to think about this might be to consider what would happen if the ball closes the switch, but the battery is dead. Do you think the electric motor would still turn?
  4. Jul 24, 2012 #3


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    Well a good example of conversion of mechanical to electrical energy is a generator; and a good example of conversion of electrical to mechanical energy is a motor. In your case, mechanical energy (the rolling ball) is ultimately converted to mechanical energy (the spinning fan). I don't believe you can say directly that when the switch is hit, mechanical energy is converted to electrical energy. That is still a mechanical form of work. What if the switch was faulty? IMHO. These definitions of conversions of energy types and forms are debatable. Someone else I am sure will have a different opinion.
  5. Jul 24, 2012 #4
    When the ball hits the switch, is the act of hitting the switch considered mechanical to electrical
    Normally a switch is fitted with a restoring spring. It is conversion of kinetic to potential energy of the spring.
  6. Jul 25, 2012 #5
    " When the ball hits the switch, is the act of hitting the switch considered mechanical to electrical"

    The reason I don't think it is, is because if that was true, and there was a conversion going on, then the harder the switch is pressed, the more electrical energy would be output due to conservation of energy.

    I believe that it is mechanical to mechanical, and then when the switch is pressed, the chemical potential of the battery is able to be converted to electrical, which then is converted to mechanical energy via the motor.

    Also, my example of mechanical to electrical would be something like a windmill or a water wheel. And those two are NOTHING like a ball hitting a switch. In both of those, the more wind or water (mechanical energy) that turns the windmill or water wheel, the more electrical energy that is output. That follows conservation of energy so I think those are good examples.

    Again though, I'm not the expert here and I'm sure someone has a much better answer than me.
  7. Jul 25, 2012 #6


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    The ball hitting the switch is NOT a conversion of kinetic to electrical energy. It is a transfer of kinetic energy from the ball to the switch, that is it. This energy is ultimately absorbed into whatever the switch is connected to, such as the frame or wall of the device.
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