Determine the magnitude of the torque

In summary, the problem involves a person holding a 25.0 N weight with a shoulder-to-elbow length of 26.0 cm and an elbow-to-wrist length of 22.5 cm. The weight is located 7.5 cm from the person's wrist. Using the equation for torque, t = lF, the magnitude of torque about the elbow is found to be 752.5 N*cm and about the shoulder is 1403 N*cm. However, the calculations were incorrect due to using the wrong units. The correct units for torque should be N*cm instead of Nm.
  • #1
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Homework Statement


A 25.0 N weight is held in the outstretched hand of a person with a shoulder-to-elbow length of 26.0 cm and an elbow-to-wrist length of 22.5 cm. The center of the weight is 7.5 cm from the person's wrist. A) Determine the magnitude of the torque about the elbow produced by the weight and B) Determine the magnitude of the torque about the shoulder produced by the weight.

http://educog.com/res/fsu/capalibrary/24equilibrium/Graphics/prob22a.gif​
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Homework Equations


Well, I can think of a few ways to solve for torque:

t = lF
tnet = I[tex]\alpha[/tex]
tnet = I[tex]\alpha[/tex]
(I = mr2)
(F = ma)

The Attempt at a Solution


Alright, well, for the first equation I knew that t = lF, where l is the lever arm distance and F is the force in Newtons.
l = 30.1 (a), 56.1(b)
F = ma
F = 2.55 x 9.81 = 25 (given)
t = 25 x 30.1 [56.1]
t = 752.5 NM [1403 NM]
Something is clearly not right here, help! I can tell I'm missing something basic, but I don't know what.
 
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  • #2


Check your units.
 
  • #3


Centimeters? Was it centimeters the whole time?
 
  • #4


It wasn't because you used Nm for the torque when it should be N*cm.
 
  • #5


No, that's what I meant. I hadn't noticed that it was cm instead of m! Thank you!
 

Related to Determine the magnitude of the torque

1. What is torque?

Torque is a measure of the force that causes an object to rotate around an axis or pivot point.

2. How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the axis or pivot point to the point of application of the force.

3. What is the unit of torque?

The unit of torque is newton-meters (Nm) in the SI system and foot-pounds (ft-lb) in the imperial system.

4. How does the position of the force affect the magnitude of torque?

The magnitude of torque is directly proportional to the perpendicular distance between the axis of rotation and the line of action of the force. The greater the distance, the greater the torque.

5. What factors can affect the magnitude of torque?

The magnitude of torque can be affected by the amount of force applied, the distance from the axis of rotation, and the angle of application of the force. Additionally, the type of force (such as a push or a pull) and the direction of rotation can also affect the magnitude of torque.

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