Momentsand Forces acting on a ruler

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In summary: It comes from the angle A the ruler makes with the horizontal. The greater the angle, the greater the horizontal component of the force provided by the Newton meter. Therefore, the force provided by the Newton meter has increased compared to when the ruler was horizontal. In summary, the force T needed to keep the ruler horizontal is 1.25N, but when the ruler is at an angle A, the force provided by the Newton meter has increased due to the horizontal component of the force.
  • #1
sarahcate
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I have a question about moments a forces acting on a meter ruler.

"A meter ruler of weight 1.0N is pivoted on a nail passing through a hole drilled at the 10cm mark. A weight of 3.0N is suspended at the 30cm mark. A Newton meter supports the ruler at the 90cm mark so that it is horizontal.
a) use the principle of moments to calculate the magnitude of force T needed to keep the ruler horizontal.
b)the Newton meter is raised until the rule makes an angle A with the horizontal. Without doing any further calculations copare the magnitude of the force provided by the Newton meter in this new positionwith the force T when the rule was horizontal. Explain your answer."

For part a I had (0.2 x 3) + (0.4 x 1) = 0.8T
to give T = 1.25N

For part b I am confused. Intuitively I think the force should have increased but I'm not really sure why and since none of the distances have changed and the weights are the same I don't how it can have changed.

Please help!
 
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  • #2
Sarahcate said:
I have a question about moments a forces acting on a meter ruler.

"A meter ruler of weight 1.0N is pivoted on a nail passing through a hole drilled at the 10cm mark. A weight of 3.0N is suspended at the 30cm mark. A Newton meter supports the ruler at the 90cm mark so that it is horizontal.
a) use the principle of moments to calculate the magnitude of force T needed to keep the ruler horizontal.
b)the Newton meter is raised until the rule makes an angle A with the horizontal. Without doing any further calculations copare the magnitude of the force provided by the Newton meter in this new positionwith the force T when the rule was horizontal. Explain your answer."

For part a I had (0.2 x 3) + (0.4 x 1) = 0.8T
to give T = 1.25N

For part b I am confused. Intuitively I think the force should have increased but I'm not really sure why and since none of the distances have changed and the weights are the same I don't how it can have changed.

Please help!
Since it is still supporting the same weight, the vertical component of force must be the same. Now, the horizontal component is non-zero. what does that tell you about the magnitude of the force?
 
  • #3
If there is now a horizontal component the force must have increased to include this.

Where does the horizontal component come from?
 

1. What is a moment?

A moment is a measure of the turning effect of a force. It is calculated by multiplying the force applied to an object by the perpendicular distance from the point of rotation to the line of action of the force.

2. How are moments and forces related?

Moments and forces are directly proportional to each other. This means that as the force acting on an object increases, the moment also increases. Conversely, if the force decreases, the moment also decreases.

3. What is the significance of the point of rotation in moments?

The point of rotation, also known as the pivot point, is where the ruler is being supported or fixed. It is important because it determines the direction of the moment and can greatly affect the stability of the ruler.

4. How does the weight of the ruler affect the moments and forces acting on it?

The weight of the ruler can affect the moments and forces acting on it, especially if the ruler is not balanced or is being used on an incline. The weight of the ruler adds to the downward force acting on the pivot point, which can change the direction and magnitude of the moment.

5. Why is it important to understand moments and forces acting on a ruler?

Understanding moments and forces acting on a ruler is important in order to accurately predict its behavior and stability. It can also help in designing structures or machines that utilize moments and forces to function properly and safely.

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