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I'm not sure if I approached this problem correctly and would like some assistance.
An elevator with a total mass of 800 kg is moving downward at 6 m/s. It slows to
a stop with constant acceleration in 3 seconds.
a) Find the tension T in the supporting cable while the elevator is brought to
a rest.
b) A 50.0-kg man stands on a bathroom scale while riding on the elevator.
What is the reading on the scale as it is brought to a halt?
c) After the stop, the elevator starts to move down – initially with 1 m/s2
acceleration. What is the reading of the weighing scale?
ƩF=ma
For a), I wrote ƩF=ma and I considered going up to be positive My equation was T - mg = ma. I ended up with T = m(a + g) for finding the tension. I saw that the elevator was being brought to rest so I figured that the acceleration would be zero and ended up with T = mg which was 7,840 Newtons.
For b) I drew a free-body diagram of the man and the forces acting on him which were the normal force and mg. I wrote ƩF=ma and my equation was N-mg = 0 which gave me N = mg which was 490 Newtons.
For c), I did pretty much the same thing as b), except my equation was N = m(a + g). I plugged in the given a and g and ended up with N= 440 Newtons.
Just looking to see if I approached this problem correctly. I can't help but think I did it wrong because I didn't utilize the given 6 m/s at all. Any help is greatly appreciated.
Homework Statement
An elevator with a total mass of 800 kg is moving downward at 6 m/s. It slows to
a stop with constant acceleration in 3 seconds.
a) Find the tension T in the supporting cable while the elevator is brought to
a rest.
b) A 50.0-kg man stands on a bathroom scale while riding on the elevator.
What is the reading on the scale as it is brought to a halt?
c) After the stop, the elevator starts to move down – initially with 1 m/s2
acceleration. What is the reading of the weighing scale?
Homework Equations
ƩF=ma
The Attempt at a Solution
For a), I wrote ƩF=ma and I considered going up to be positive My equation was T - mg = ma. I ended up with T = m(a + g) for finding the tension. I saw that the elevator was being brought to rest so I figured that the acceleration would be zero and ended up with T = mg which was 7,840 Newtons.
For b) I drew a free-body diagram of the man and the forces acting on him which were the normal force and mg. I wrote ƩF=ma and my equation was N-mg = 0 which gave me N = mg which was 490 Newtons.
For c), I did pretty much the same thing as b), except my equation was N = m(a + g). I plugged in the given a and g and ended up with N= 440 Newtons.
Just looking to see if I approached this problem correctly. I can't help but think I did it wrong because I didn't utilize the given 6 m/s at all. Any help is greatly appreciated.
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