Physics Review Question Unit: work and energy Year: 1997 Question#: 20 Question: A motor having a power rating of 8.1 * 104 watts is used to operate an elevator with a weight of 1.8 * 104 newtons. What is the maximum weight this motor can lift at an average speed of 3.0 meters per second (1 ) 6.0 * 103 N (2 ) 1.8 * 104 N (3 ) 2.4 * 104 N (4 ) 2.7 * 104 N What is this question really asking? Explanation by: Ajemo H [ Return to question menu ] Answer 1 6.0 * 103 N INCORRECT The equation should be P=Fv. Where P= power, v=avg velocity, and F=force. return to top Answer 2 1.8 * 104 N INCORRECT The equation should be P=Fv. Where P= power, v=avg velocity, and F=force. return to top Answer 3 2.4 * 104 N INCORRECT The equation should be P=Fv. Where P= power, v= avg velocity, and F=force. return to top Answer 4 2.7 * 104 N CORRECT The equationto use is P=Fv. Where P= power, v=avg velocity, and F=force. If you plug 81000 watts in for power, and 3.0 meters per second in for the avg velocity, then you will get an answer of 27000 N. To put this number into scientific notaion you take the decimal place and move it to one place before the last digit. Then you count the number of places you ha to mave the decimal place, and that is the power to which you will raise ten to in the notation. return to top What's this question really asking? This question is asking if you know how to use the formulas for Power that you are given for the test. It also asks if you know your scientific notation. return to top |
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