The Student Room Group
Reply 1
Is the answer 6000N?
Tension would be the resultant + gravity. Since tension is the force needed to accelerate the lift by 2ms^-2 whilst it is under gravity.
Reply 3
Great, thanks. Yes - its 6000N.
Reply 4
Original post by liamsullivan
I'd be grateful if you could help me with this question. I thought to use F=ma, but was wrong. Thanks!

A lift and it's passengers with a total mass of 500kg accelerates upwards at 2ms^-2. Assume that g-10 ms^-2. What is the tension in the cable that holds the lift to the ceiling?


I think F=ma is the right approach, a tip is to draw a force diagram with all the known forces and the resultant. Also write the other things you know like acceleration on the force diagram so it is clearer if you haven't already.

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Reply 5
Original post by liamsullivan
Great, thanks. Yes - its 6000N.

If you sub the forces into F=ma:
T-500g = 500 * 2
T=6000N
Reply 6
Original post by ak111
If you sub the forces into F=ma:
T-500g = 500 * 2
T=6000N

the lift accelerates upwards so wouldn't acceleration be negative .
Original post by Sujit123
the lift accelerates upwards so wouldn't acceleration be negative .

Lmao this was posted 5 years ago but I love the dedication dude!
Original post by Sujit123
the lift accelerates upwards so wouldn't acceleration be negative .

Hi Sujit123, welcome to TSR. :smile:
As you are new, I would make an exception to explain the problem in "detail" and then the thread will be locked.

Which acceleration do you mean to be negative? (2 m/s^2 or 10 m/s^2)
In such problem, you are allowed to take upward as positive or downward as positive.
It is your own choice.
Say we take upward as positive:
Then the acceleration of 2 m/s^2 needs to be positive while the acceleration due to gravity that is 10 m/s^2 needs to be negative.

Spoiler



However, if we take downward as positive:
Then the acceleration of 2 m/s^2 needs to be negative while the acceleration due to gravity that is 10 m/s^2 needs to be positive.

Spoiler


You would arrive at the same magnitude of tension with a different sign because tension is upward in this problem.


Hope this makes sense.

Please do not post on a thread that is more than 2 years. You can always create a new thread and post the link in the new thread as a reference to your problem.

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