3 09 m/ Need Help? asWse points 1 Previous Answers SerPSE9 5 P051 M My Noes Ask

Question

3 09 m/ Need Help? asWse points 1 Previous Answers SerPSE9 5 P051 M My Noes Ask Yor his a 780kg man standing on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of Les m s i, asso·nnes it constant speed for the next 5.00s. The elevator then undergoes a uniform acceleration in the negative y direction for 1.10 s and comes to rest a) what does the spring scale register before the elevator starts to move? 764 4 (b) What does the spring scale register during the first o.sso s? 497 78 Your response differs from the correct answer by more than 10%. Double check your calculations, N (c) what does the spring scale register while the elevator is traveing at constant speed? 764.4 d) what does the spring scale register during the time it is slowing down? differs from the correct answer by more than 10% Double deck your calculations, N Need help? unanaLmm. Save Progross Practice Another Version bMy Notes Ask You 7 8 9 5 6 3

Explanation / Answer

Before the elevator starts moving, Reading of the elevator will be only the weight of the man only, i.e.

a) W = mg

W = 78 x 9.8 = 764.4 N

b.) a = v/t = 1.88/0.55 = 3.42m/s2
W - mg = ma

W = m (g + a) = 78*(9.8 + 3.42) = 1031.02 N

c.) W - mg = ma
W - mg = 0

W = mg

W = 78 x 9.8 = 764.4 N

d.) a = v/t = 1.88/1.10=1.71m/s2
W - mg = - ma

W = m (g - a) = 631.09 N

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