Force of a hinge on a hinged beam

  • Thread starter Thread starter Becca93
  • Start date Start date
  • Tags Tags
    Beam Force Hinge
AI Thread Summary
A 26.6 kg beam is hinged to a wall and supported by a cable at a 90° angle, inclined at 13.3° to the horizontal. The discussion focuses on calculating the horizontal component of the force exerted by the hinge, emphasizing that net torque and net force must equal zero for equilibrium. Participants suggest summing moments about the hinge to find the tension in the cable, noting that the beam's weight acts at its midpoint. There is confusion regarding the use of sine and cosine in calculations, and the necessity of the beam's length is debated. Ultimately, it is suggested that the beam length may not be required to solve the problem.
Becca93
Messages
84
Reaction score
1
Homework Statement

A 26.6 kg beam is attached to a wall with a hinge and its far end is supported by a cable. The angle between the beam and the cable is 90°. If the beam is inclined at an angle of theta=13.3° with respect to horizontal, what is the horizontal component of the force exerted by the hinge on the beam? (Use the 'to the right' as + for the horizontal direction.)

Hint: The Net torque and the Net Force on the hinge must be zero since it is in equilibrium.

What is the magnitude of the force that the beam exerts on the hinge?

(Image attached)

The Attempt at a Solution



I already knew that the net force and net torque would be zero, so I set clockwise and counter clockwise torque equal to each other

τcw = τccw
Fdsinθ = Fdsinθ

And this is where I ran into trouble. Length of the beam is never given. I'm not really sure what angles to use where, and while I know that the force the beam exerts on the wall/hinge is equal and opposite to what the wall/hinge exerts on the beam, I'm not sure how to find it.

To find the magnitude of force in the second half of the problem, you would just take magnitude = √(Fx^2 + Fy^2), correct?

Any advice?
 

Attachments

  • prob19a_beamhinge1.gif
    prob19a_beamhinge1.gif
    1.8 KB · Views: 1,200
Physics news on Phys.org
It is best to first find the tension force in the cable by summing moments about the hinge.. the beams weight acts at midpoint and moment is force times perpendicular distance.. Your sohcahtoa is off. Try again.
 
PhanthomJay said:
It is best to first find the tension force in the cable by summing moments about the hinge.. the beams weight acts at midpoint and moment is force times perpendicular distance.. Your sohcahtoa is off. Try again.

Okay, I understand that I need to use cos instead of sin, but I still don't understand what to do without the length of the beam.
 
Sum moments of the forces about the hinge. aybe you don't need to know thw beam length.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top