How Far Can Professor Fich Move Before Exceeding the Rope's Tension Limit?

  • Thread starter Thread starter bluejay1
  • Start date Start date
  • Tags Tags
    Sign Torque
AI Thread Summary
The discussion focuses on a physics problem involving a wooden sign supported by a hinge and a rope, with Professor Fich hanging from it. The conditions for static equilibrium are established, requiring the calculation of horizontal and vertical force components at the hinge, as well as the tension in the rope. Participants express difficulty in setting up the torque equations and moment arms, particularly regarding the angles and forces acting on the sign. A suggestion is made to choose a reference point for torque calculations to simplify the equations. The conversation emphasizes the importance of correctly identifying forces and their respective moments to solve for how far Professor Fich can move without exceeding the rope's tension limit.
bluejay1
Messages
5
Reaction score
0

Homework Statement



3B. A uniform wooden sign of mass 4.0 kg hangs beside a building wall. The sign is 2.00 m
high and 4.00 m wide. It is supported by a hinge at P, that is midway up one
edge, and by a light rope that is attached exactly three-quarters of the distance across the
upper edge. The rope makes an angle of 20.0 degrees with the horizontal.

(b) Write the conditions for static equilibrium of the sign and solve for the horizontal (H) and vertical (V) components of the force at P, and solve for the rope tension (T)

(c) Later, Prof. Fich of mass 90.0 kg climbs out of a window just below the sign, reaches up and grabs onto the bottom portion of the sign and, while hanging from the sign, begins to move away from the building. If the rope can only support a maximum tension of 1500 N, how far can Prof. Fich move away from the building ?

Homework Equations



net torque=0
Fnety=0
Fnetx=0

The Attempt at a Solution


I have the force equations set up.
Tsin20+Fpv-4g=0
Tcos20=Fph
I am having trouble setting up the torque. For the moment arm, can you go through the sign? I can't get the moment arms and angles set up.
So far I have
Tsin38.4(sqroot10)=mg(2)
Is this right?
(The three lines I've drawn on the sign are what I think the 2 moment arms are, and also the vector for Fg)
 

Attachments

  • sign.jpg
    sign.jpg
    9.7 KB · Views: 1,112
Last edited:
Physics news on Phys.org
bluejay1 said:
I am having trouble setting up the torque. For the moment arm, can you go through the sign? I can't get the moment arms and angles set up.
So far I have
Tsin38.4(sqroot10)=mg(2)
Is this right?
(The three lines I've drawn on the sign are what I think the 2 moment arms are, and also the vector for Fg)

While I can't view your attachment yet, I think there is enough information in the worded description to see what is being asked.

For the torques, you just need to choose a reference point from which to calculate torques due to the forces that are present. Hint: it's generally useful to choose a point where 1 or more of the forces are acting. That way, those forces will have zero torque and the equation will be simpler to work with.

EDIT: Okay, I can view your attachment now. Your torque equation looks right.
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanged mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top