Ex-Gov. Phil Bredesen takes the elevator down from the Neyland Stadium skyboxes.

Question

Ex-Gov. Phil Bredesen takes the elevator down from the Neyland Stadium skyboxes. Having earned a physics degree from Harvard, the good ex-governor makes some measurements while riding down the elevator. He stands on a scale and notes various readings. The ex-governor has mass of 80 kg. The mass of the elevator and the other occupants is 790 kg EXAMPLE EXAMPLE NOTES IMAGES DISCUSS EXAMPLES UNITSSTATS HELP Part Description Answer Chk History As the elevator starts down, the scale Phil is standing on reads 427 N. Determine the magnitude of the acceleration of the elevator (include units with answer) 12.5 pts. 100% # tries: 0 Show Details Format Check 2% try penalty Hints: 1,0 Determine the tension in the cable supporting the elevator as the elevator starts down. (include units with answer) 12.5 pts. 100% # tries: 0 Show Details Format Check 2% try penalty

Explanation / Answer

A. Fnet = N - m g = m a

N = 427 N  

427 - (80 x9.8) = 80 a

a = - 4.46 m/s^2

minus sign indicates that acceleration is downwards.
magnitude = 4.46 m/s^2

B. T - (m + M)g = (m + M) a

T = (80 + 790)(9.8 - 4.46)

T =4643.6 N  

C. 946 - (80 x9.8) = 80 a

a = 2.02 m/s^2

D. T = (790 + 80) (9.8 + 2.02)

T = 10288 N

E. d1 = v0 t + a t^2 / 2

d1 = 0 + (4.46 x 1.5^2 / 2) = 5 m

v1 = v0 + a t = 6.69 m/s

d2 = (6.69 x 7.4) = 49.5 m

vf^2 - vi^2 = 2 a d

0^2 - 6.69^2 = 2(-2.02) d3

d3 = 11 m

d = d1 +d2 +d3 = 65.6 m

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