# Turning effect of forces and min force to find the moment of force X about A,is the working
20x1.4=0.8X
X=35Nm clockwise.

and what does it mean when the question asks "what is the minimum force X that must be applied in order to stop the door from turning?"

does that mean it has to be in equilibrum?

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Doc Al
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to find the moment of force X about A,is the working
20x1.4=0.8X
X=35Nm clockwise.
X is the force; the moment of the force is just the force times the moment arm (distance to pivot).

and what does it mean when the question asks "what is the minimum force X that must be applied in order to stop the door from turning?"
The force F exerts a moment tending to turn the door; force X must exert an opposite moment to cancel it.

does that mean it has to be in equilibrum?
Yes, rotational equilibrium.

(FYI: It's always a good idea to state the problem exactly as given.)

Yes, rotational equilibrium.

(FYI: It's always a good idea to state the problem exactly as given.)
okay the question is "what is the minimum force X that must be applied in order to stop the door from turning?"

(p.s.,i'm not quite sure as i didnt attend school today and this is part of my homework from my physics workbook)

Doc Al
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okay the question is "what is the minimum force X that must be applied in order to stop the door from turning?"
And you already solved for that force X. (Even if you didn't recognize it as such.)

oh,i see.but then the question is phrased in two parts.does this mean that i can just bring forward the answer?

Doc Al
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What are the two parts? State the complete problem exactly as given.

a) Calculate the moment of the force X about A.

b) what is the minimum firce X that must be applied in order to stop the door from turning?

Doc Al
Mentor
a) Calculate the moment of the force X about A.

b) what is the minimum firce X that must be applied in order to stop the door from turning?
Good. In the light of my previous posts, can you answer each part?

Good. In the light of my previous posts, can you answer each part?
so does that mean that both questions the answers are the same?
because you previously said that i actually answered the question without me knowing

Doc Al
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so does that mean that both questions the answers are the same?
No, the answers are not the same. The first part asks for a moment; the second part for a force.
because you previously said that i actually answered the question without me knowing
Right. You actually solved for the force (X) when you thought you had solved for the moment.

I interpret the first question as a general question that helps you answer the second question. For a force X that is a certain distance from the axis, what's the moment?

Doc Al
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