Another torque/statics problem

  • Thread starter blue2004STi
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In summary, a rock climber with a mass of 55kg is performing a lie-back climb along a fissure with a width of 0.25m. Their center of mass is 0.43m from the fissure, and the coefficient of static friction between their hands and the rock is 0.42, while it is 1.25 between their boots and the rock. To keep stable, the least horizontal pull by their hands and push by their feet must be 953.5269N, as determined by the "weight" and "torque" equations. However, without a diagram it is difficult to fully understand the problem and potential errors in calculation.
  • #1
blue2004STi
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Homework Statement


Prof. Holland, in his younger days, (when he had a mass of 55kg) is in a lie-back climb along a fissure, with hands pulling on one side of the fissure and feet pressed against the opposite side. The fissure has width w = 0.25m, and the center of mass of the climber is a horizontal distance d = 0.43m from the fissure. The coefficient of static friction between hands and rock, μhands, is 0.42, and between boots and rock, μboots is 1.25.
What is the least horizontal pull by the hands and push by the feet that will keep him stable?



Homework Equations


Weight: 0 = (Ushands*Fa + Usboots*Fb) -539N
Fb=force by boots
Fa=force by hands
Torque: 0 = Fa*Distance from CM + Fb*Distance from CM




The Attempt at a Solution


So I tried setting up an equation for the forces made by the hands and feet which was the "Weight" equation above. Then I created the "Torque" equation. I knew since the climber(Professor Holland) was in static equilibrium that the both of them had to equal zero. I solved for both of the forces and keep coming up with A=786.6369N and B=166.89N and A+B(what they're looking for)=953.5269N.

I have to submit it online and it says that the answer is not correct. What am I doing wrong? I don't understand this problem!AHHHHH!

Thanks,
Matt

oh yeah forgot, thanks in advance for the help...it's much needed.:smile:
 
Last edited:
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  • #2
We need a diagram. I can't picture at all what you mean. Not being a rock climber.
 
  • #3
13-34.jpg


Sorry about the no picture thing, hopefully this works.
 
  • #4
In the torque equation, try leaving out the u's. The force normal to the frictional force is the one causing the torque ( I think).
 
  • #5
Woops, I forgot to delete the U's from that equation when I put it up here, I'll edit the first post. I didn't include U's in torque, at least it doesn't look like I did. Sorry
 

1. What is torque and how is it related to statics?

Torque is a measure of the turning or twisting force applied to an object. In the context of statics, torque is related to the equilibrium of a system. When all forces acting on an object are balanced, the net torque is equal to zero, resulting in a state of static equilibrium.

2. How do you calculate torque in a statics problem?

To calculate torque, you need to know the magnitude of the force applied and the distance from the point of rotation to the point where the force is applied. The formula for torque is T = F x d, where T is torque, F is force, and d is distance. The unit for torque is Newton-meters (Nm) in the metric system and foot-pounds (ft-lb) in the imperial system.

3. Can you give an example of a torque/statics problem?

One example of a torque/statics problem is balancing a seesaw. In this scenario, the weight of each person sitting on the seesaw creates a force that is balanced by the distance from the pivot point. If one person moves closer to the pivot point, their weight exerts a smaller torque compared to the person sitting farther from the pivot point with a greater weight.

4. How does the direction of force affect torque in a statics problem?

The direction of force is crucial in determining the direction of torque. If the force is applied perpendicular to the distance from the pivot point, the torque will be at its maximum. If the force is applied parallel to the distance, the torque will be zero. In general, the greater the angle between the force and the distance, the lower the torque will be.

5. What is the principle of moments in statics?

The principle of moments states that the sum of clockwise moments must be equal to the sum of counterclockwise moments for a system to be in static equilibrium. This principle is based on the fact that the net torque must be zero for a system to remain balanced and stationary. It is a fundamental concept in solving torque/statics problems.

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