# Point mechanics -- Tension in a rope from a hanging mass

• duchuy
In summary, the question is asking for the tension of a rope knowing the value of acceleration due to gravity. However, without knowing the mass, the question cannot be answered numerically. The tension is equal to the weight multiplied by the acceleration of gravity. It is unclear if an algebraic answer is expected. It is recommended to clarify with the teacher for full credit.

#### duchuy

Homework Statement
Rope tension
Relevant Equations
t = ma
Hi,
I'm being asked to determine the tension of a rope only knowing that g = 9.8 m.s-2. I understand that in order to calculate tension, I would need to multiply mass with acceleration. But i don't understand how i would in this case. This is the question for reference. Thanks for your help.
And 9.8N isn't correct so I am confused..

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What is the value of the mass in Kg?

Is this all that is given? The tension depends on the mass and if the mass is not given, then you cannot find a numerical answer for the tension.

Lnewqban said:
What is the value of the mass in Kg?
This why I don't understand the question because the mass is not given.

kuruman said:
Is this all that is given? The tension depends on the mass and if the mass is not given, then you cannot find a numerical answer for the tension.
I was thinking if there is somehow i could write the tension algebraically somehow I don't know?

duchuy said:
I was thinking if there is somehow i could write the tension algebraically somehow I don't know?

If the mass is not given, then the question cannot be answered. If the mass is not accelerating, the tension is equal to the weight ##mg## which is the product multiplied by the acceleration of gravity. I doubt that an algebraic answer is expected. You are told to write the answer to two significant figures (2 chiffres significants) which means numbers, n'est-ce pas?

Lnewqban
kuruman said:
If the mass is not given, then the question cannot be answered. If the mass is not accelerating, the tension is equal to the weight ##mg## which is the product multiplied by the acceleration of gravity. I doubt that an algebraic answer is expected. You are told to write the answer to two significant figures (2 chiffres significants) which means numbers, n'est-ce pas?
Yess with 2 significant figures ( I didn't know that's how it was called btw so thanks a lot). So this might be a mistake from the prof right? Cuz I was thinking something like m.9.8 but it's not correct.

Was there any text above this Question #1? Something like, "in the following questions, use m = 2kg"...

EDIT. Just realized that you have to enter your answer into a computer. So my suggestion (below) is inapplicable. Sorry.

If you are sure that you have the full, correct question, and that no value of mass is given, you could write something like this (but in French I presume!):

"Since no value of mass is given, for the purpose of showing the method I will take the mass to be 17kg."

And then you can complete the question.

You should then get full credit.

Steve4Physics said:
You should then get full credit.
Not if the algorithm that scores the answer expects a specific numerical value. Better ask the person who assigned the problem for clarification.

On edit:
Steve4Physics said:
EDIT. Just realized that you have to enter your answer into a computer. So my suggestion (below) is inapplicable. Sorry.
And I just realized that you have rescinded your suggestion which makes my comment (above) unnecessary. Sorry.

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Ok I see. Thanks so much for the help!

Delta2 and kuruman