 4
 1
 Homework Statement

A lift in a mine shaft takes exactly one minute to descend 500m. It starts from rest, accelerates uniformly for 12.5 seconds to a constant speed which it maintains for some time and then decelerates uniformly to stop at the bottom of the shaft.
The mass of the lift is 5 tonnes and on the day in question it is carrying 12 miners whose average mass is 80kg.
i) Sketch the speedtime graph of the lift.
ii) During the first stage of the motion the tension of the cable is 53 640N. Find the acceleration of the lift during this stage.
iii) Find the length of time for which the lift is travelling at constant speed and find the final deceleration.
iv) What is the maximum value of the tension in the cable?
v) Just before the lift stops one minor experiences an upthrust of 1002N from the floor. What is the mass of the miner?
 Homework Equations

Suvat equations.
F=mg + ma
As I mentioned I am self tutoring myself on a subject I studied 20 years ago.
I'm sure I can answer all the questions apart from question (iii). I think i'm supposed to use a simultaneous equation. But I need to answer question (iii) to answer the rest.
Any help please?
I'm sure I can answer all the questions apart from question (iii). I think i'm supposed to use a simultaneous equation. But I need to answer question (iii) to answer the rest.
Any help please?