Solving Lever (Moment) Homework Problem

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In summary, the question is asking for the distance from one end of a 10 m long, 50 kg pole where an upward force of 400 N needs to be applied in order to keep the pole horizontal, using the other end as a fulcrum. This is to be solved using the concept of moments, with the weight of the pole being 500 N and the upward force applied by one brother being 100 N.
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luysion
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Homework Statement


A uniform 10 m long, 50 kg pole is lying on the ground. You get your little brother to lift at one end with an upward force of 100 N. How far from the other end will you need to lift so the pole stays horizontal (in m)? [Hint: Using your little brother as the fulcrum, what upward force, in N will you need to apply?]


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The Attempt at a Solution



Hi, I am really confused as to how to answer this. I know its to do with moments but i don't understand how to use the brother as the fulcrum because how much force does the other brother have to apply? the question doesn't say
 
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  • #2
I think this is a poorly conceived question.
The other brother must lift with at least a force that will, when combined with the first brother, equal the weight of the the pole. In round figures (taking g as 10m/s²)
The weight is 500N and the one guy has an upward force of 100N, so you need at least 400N upwards. The question is, where do you apply that 400N to keep the pole horizontal; that is, there is no overall turning moment.
(At least that's what I think they mean!)
 

What is a lever?

A lever is a simple machine consisting of a rigid bar that rotates around a fixed point called a fulcrum. It is used to amplify or redirect the force applied to one end, making it easier to lift or move objects.

What is a moment in the context of a lever?

In the context of a lever, a moment refers to the turning effect of a force around the fulcrum. It is calculated by multiplying the force applied to the lever by the perpendicular distance from the fulcrum to the point where the force is applied.

How do I calculate the moment of a lever?

To calculate the moment of a lever, you need to know the force applied to the lever and the distance from the fulcrum to the point where the force is applied. The moment is then calculated by multiplying the force by the distance.

What is the principle of moments?

The principle of moments states that for a lever to be in equilibrium, the sum of the clockwise moments must be equal to the sum of the counterclockwise moments. This means that the lever will not rotate as long as the moments on both sides of the fulcrum are balanced.

What are some real-life applications of levers?

Levers have many practical applications in our daily lives, such as using a crowbar to lift heavy objects, using scissors to cut paper, and using a seesaw in a playground. They are also used in more complex machines, such as cranes, wheelbarrows, and pliers.

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