physics questions !?

[pimpdaddy5822]

1. How much tension must a rope withstand if it is used to accelerate a 1200 kg car vertically upward at 0.90 m/s^2



2. A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.63 of the person's regular weight. Calculate the acceleration of the elevator, and find the direction of acceleration.

[rijim2001]

1) Add the weight of the car (W=mg) + the accelerating force (F=ma)

mg + ma = T
12000(9.8) + 12000(0.90) = 128,400 N = T
2) Subtract
W-ma = 0.63W
mg - ma = 0.63mg
g - a = 0.63 g
a = g - 0.63 g

a = 3.62 m/s/s downward