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Help with physics homework
A 65 kg man stands on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of 1.2 m/s in 0.89 s. It travels with this constant speed for 5.0 s, undergoes a uniform negative acceleration for 1.2 s, and comes to rest. What does the spring scale register in each of the following time intervals?
(a) before the elevator starts to move N (b) during the first 0.89 s N (c) while the elevator is traveling at constant speed N (d) during the negative acceleration N |
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In each case you get your answer is found using F = ma, where 'a' (acceleration) has two components: the acceleration due to gravity - called 'g' - plus the acceleration of the elevator - call it a_e. Hence the force with which the man's body pressses down on the scale is equal to F = m(g+a_e)
In question (a) the acceleration due to the elevator is 0. So what do you get for F? In question (b) you need to add the acceleration of the elevator a_e, which you can determine based on the data you've been given. You add a_e because the acceleration is upward, so it takes a greater force to be applied between the scale and the man to accelerate him upward. Can you finish it out from here? |
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