As shown above, three blocks are tied in a vertical line bythree strings, and th

Question

As shown above, three blocks are tied in a vertical line bythree strings, and the top string is tied to the ceiling of anelevator. Use g = 10 m/s2. What is themagnitude of the tension in string 3if the elevator is...

(a) at rest?

(b) moving at a constant velocity of 4.00 m/s up?
2

(c) accelerating up at 3.00m/s2?

Explanation / Answer

For block 1 we have     T1 - T2 - w1 = m1a          ............1 For block 2     T2 - T3 - w2 = m2a         .........2 For block 3 we have     T3 - w3 = m3a              ........3 ---------------------------------------------------------------------------------------------------------- a) when the elevator is at rest        a = 0 ==> T3 = w3 = 50 N        T2 = T3 + w2 = 50 + 30 =80N          T1 = T2 + w1 = 80+ 20 = 100 N b) when the elevator is moving with constant velocity, then        a = 0 ==> T3 = w3 = 50 N        T2 = T3 + w2 = 50 + 30 =80N          T1 = T2 + w1 = 80+ 20 = 100 N c) when elevator accelerating upward , a = - 3.0m/s2         T3 = 50 - 15 = 35 N         T2 = 65 - 9 = 56 N         T1 = 76 - 6 = 70 N d) similarly solve the tension from above three relations using a =+ 2.0 m/s2

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