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# Forces in M1 watch

1. I have repeatedly tried to find a way to understand "forces in a lift" questions and have repeatedly failed. Can anyone help?
2. the reaction R of the floor on the passenger causes most problems...

if the lift has acceleration a then the net force on the passenger divided by the mass of the passenger ( including any parcels etc being carried ) must equal a.

the net force will be mg - R if the acceleration is downwards, and R - mg if the acceleration is upwards.
3. (Original post by kingflute)
I have repeatedly tried to find a way to understand "forces in a lift" questions and have repeatedly failed. Can anyone help?
You need to understand the interactions of Newton's laws correctly. There's really nothing specific to forces in a lift. Maybe you could take a look at the Khan academy videos on Newton's laws?

It would be easier to explain if you put up a particular problem that you're having trouble with, too.
4. (Original post by atsruser)
You need to understand the interactions of Newton's laws correctly. There's really nothing specific to forces in a lift. Maybe you could take a look at the Khan academy videos on Newton's laws?

It would be easier to explain if you put up a particular problem that you're having trouble with, too.
It is as much knowing when to use overall forces or forces on an object in the lift or the lift itself, as anything else
5. (Original post by kingflute)
It is as much knowing when to use overall forces or forces on an object in the lift or the lift itself, as anything else
This is too vague for me to comment on meaningfully. Put up a specific question, then someone can explain how things fit together more clearly. However, my previous comments still stand: you need to learn, and understand how to use, Newton's laws in general, not in some specific lift problem.

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