- #1
Tycho
- 23
- 0
A 1260kg freight elevator is supported by a steel cable of diameter 34.9mm. It is loaded with a crowd of people collectively having a mass of 2850kg and it is descending.
a) What is the strain on the cable while the elevator is descending at the constant speed of 2.30 m/s?
b) What is the strain in the cable when it is brought to a stop in 0.600s?
okay this doesn't seem to be very hard, but as i tried to do it, i just keep getting stuck.
okay firstly: strain.
i only know of 2 types of strain: tensile, and shear. this definitely isn't a shear strain problem since the force applied is not directed parallel to the surface.
that leaves tensile strain. Tensile strain is (the change in length in response to applied stress) / (relaxed length) is it not? But if this is what i am supposed to use, shouldn't the problem have given me an initial legth of the cable? This leads me to believe that i am confused on the concept of strain. Is there a different type of strain that i am missing, or should there be another step?
Thanks physics gurus!
a) What is the strain on the cable while the elevator is descending at the constant speed of 2.30 m/s?
b) What is the strain in the cable when it is brought to a stop in 0.600s?
okay this doesn't seem to be very hard, but as i tried to do it, i just keep getting stuck.
okay firstly: strain.
i only know of 2 types of strain: tensile, and shear. this definitely isn't a shear strain problem since the force applied is not directed parallel to the surface.
that leaves tensile strain. Tensile strain is (the change in length in response to applied stress) / (relaxed length) is it not? But if this is what i am supposed to use, shouldn't the problem have given me an initial legth of the cable? This leads me to believe that i am confused on the concept of strain. Is there a different type of strain that i am missing, or should there be another step?
Thanks physics gurus!