Calculating Leverage and Mechanical Advantage

In summary, the two brothers are using a lever with a 20kg, 3.5m plank and a fulcrum 0.75m away from the load mass. With a downward force of 210N, they are able to move the load mass. To find the upward force exerted on the large mass, the equation Fede= FLdL is used, with 210N as the Fe and 2.75 as the de set equal to FL multiplied by 0.75 for dL. This results in the upward force being equal to the weight of the load mass. The mechanical advantage of the lever can be determined by F_L / F_e, and in this case, it would be greater
  • #1
Ignoramus
18
0
1. A pair of brothers have a 20kg, 3.5m plank they want to use as a lever. They use a fulcrum which is 0.75m from the load mass. If they push down one end of the lever with a force of 210N, then they can move the Load mass away. What is the upward force exerted on the large mass? If the mechanical advantage is defined as a ratio of resistance force compared to the effort force, how much mechanical advantage is gained by the lever?



Homework Equations


Fede= FLdL


3. I used the 210N as the Fe, and 2.75 as the de set equal to FL multiplied by 0.75 for dL Then I solve for the FL. I'm not sure if the answer I get is the upward force, though I would assume it is...As for the second question, I have no idea where to begin on that. Thanks!
 
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  • #2
It may be a little more complicated.

The plank has mass. And assuming it has uniform density over its length then you have an unbalanced weight just from the plank alone don't you?
 
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  • #3
you forgot to consider the torque due to the weight of the 20 kg lever itself. What does the sum of torque equation tell you about the direction of the force at the end you label as "L"? Mechanical advantage is just F_L / F_e.
 
  • #4
Our teacher is notorious for giving us variables that are not needed, so I'm doubting the mass of the plank matters. Plus the fact that we've never had to mess with the mass of the lever itself. Although, the mass is 210 N, so dividing by 9.8,you find the mass of the load is greater than the plank.

I have no idea what the sum of torque equation is, since we just started on simple machines :\
 
  • #5
Unfortunately it does matter, the reputation of your teacher not withstanding.

The effect is sizable. Because basically you have the distance of the center of mass acting at a distance from the fulcrum. That looks like 20*9.8 N acting at about a meter from the fulcrum.
 
  • #6
So...what should I do?


Help :(
 
  • #7
Draw a diagram.

Add up your torques.

The total net torque/distance to the mass is the force delivered to the mass.
 

1. What is leverage and mechanical advantage?

Leverage is the ability to amplify a force to accomplish a specific task. Mechanical advantage is the ratio of the output force produced by a machine to the input force applied to it.

2. How can I calculate leverage?

Leverage can be calculated by dividing the distance from the pivot point to the point of application of the force by the distance from the pivot point to the point of resistance.

3. What is the formula for calculating mechanical advantage?

The formula for mechanical advantage is MA = output force / input force, where MA is the mechanical advantage, output force is the force produced by the machine, and input force is the force applied to the machine.

4. What is the difference between first, second, and third-class levers?

In a first-class lever, the pivot point is between the input and output forces. In a second-class lever, the output force is between the pivot point and the input force. In a third-class lever, the input force is between the pivot point and the output force.

5. How can I use leverage and mechanical advantage in everyday life?

Leverage and mechanical advantage are used in many everyday tasks, such as using a wrench to loosen a bolt or using a seesaw on a playground. They also play a role in more complex machines, like car engines and cranes.

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