I tried to do N= m(g+a) and I got 902.9 and that answer was incorrect and I thin

Question

I tried to do N= m(g+a) and I got 902.9 and that answer was incorrect and I think I just do not know how to do this at all.

Consider a 79.0-kg man standing on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of 1.06 m/s in 0.650 s. It travels with this constant speed for the next 5.00 s. The elevator then undergoes a uniform acceleration in the negative y direction for 1.70 s and comes to rest. (a) What does the spring scale register before the elevator starts to move? Your response differs from the correct answer by more than 10%. Double check your calculations. N (b) What does the spring scale register during the first 0.650 s? (c) What does the spring scale register while the elevator is traveling at constant speed? (d) What does the spring scale register during the time it is slowing down?

Explanation / Answer

A) before moving N= mg = 79*9.8= 774.2 N

*B) during first 0.650s N= ma+mg= 79*1.6 + 79*9.8=903N a= (v-u)/t= 1.06-0/.650= 1.6m/s2

C) acceleration a=0 Hence N=mg= 774.2 N

D) acceleration a= 1.6-0/1.7= 0.941

N= mg-ma= 79*9.8 - 79*0.941= 699.84 N

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