People in Lifts

When analysing the forces on people in lifts, it is important to remember:Newton's Third Law – to every action there is an equal and opposite reaction, this means that the reaction of anybody in the lift on the lift is the same as the reaction of the the reaction of the lift on anybody in the lift. In the diagrams belowis the tension in the lift cable,is the mass of the person andis the mass of the lift

We apply

For the Person: (1)

For the lift: (2)

Typically,andare known quantities, andcan be measured. We can findand from the above simultaneous equations.

From (1)

(1) +(2) gives