# Answer to Question #727 in Mechanics | Relativity for Brian

Question #727
An elevator starts from rest with a constant upward acceleration and moves 1m in the first 1.5 s. A passenger in the elevator is holding a 9.6 kg bundle at the end of a vertical cord. The acceleration of gravity is 9.8 m/s2 . What is the tension in the cord as the ele- vator accelerates? Answer in units of N.
1
2010-10-05T19:06:49-0400
From the equation of the motion we can get the acceleration of the elevator:h = x0+ v0t + at2/2; v0=0, x0=0;thusa = 2h/t2 = 2*1/1.52 = 0.9 m/s2. Then we can find the tension in the cord:
T = mg + ma = 9.6 (9.8 + 0.9) = 102.7 N

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Assignment Expert
16.02.12, 16:06

Because we have gravity force and elevator acting on the object and gravity also contributes into value of tension

Lila
16.02.12, 02:41

why does T=mg+ma instead of just T=ma?