Author Topic: 6/17/2014 Dynamics  (Read 1580 times)

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6/17/2014 Dynamics
« on: June 17, 2014, 07:41:12 AM »
Question:

During a certain time interval, a 20-N object free-falls 10 meters. The object gains _____ Joules of kinetic energy during this interval.

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Re: 6/17/2014 Dynamics **SOLUTION**
« Reply #1 on: June 19, 2014, 08:35:21 AM »
The total amount of mechanical energy is conserved in free-fall situations (no external forces doing work). Thus, the potential energy that is lost is transformed into kinetic energy. The object loses 200 J of potential energy (PE loss = m * g * h  where the mg is 200 N (i.e., the object's weight).

Observe that a confusion of mass (~20 kg) and weight (200 N) will inevitably lead to the wrong answer.

andrei

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Re: 6/17/2014 Dynamics
« Reply #2 on: March 01, 2015, 05:34:26 PM »
Isn't mg = 20 N? So, the answer is 200 J.