- #1

lela

- 6

- 4

- Homework Statement
- A traffic light hangs from a pole as shown in Fig. 12–60. The uniform aluminum pole AB is 7.20 m long and has a mass of 12.0 kg. The mass of the traffic light is 21.5 kg.

Determine (a) the tension in the horizontal massless cable CD, and (b) the vertical and horizontal components of the force exerted by the pivot A on the aluminum pole.

(link to Fig. 12-60 https://ibb.co/YX9yTvF)

- Relevant Equations
- Newton's second law for translational and rotational motion, also think Newton's third law might be relevant.

I thought that the force by the pivot A on the pole AB would be the reaction force to the x-component of the gravitational force on AB. This would mean that the force by the pivot would be parallel to the pole, but in my notes from class the force vector seems to be more along the bisector of CÂB..

I checked in my textbook and found an example question about the force by a floor on a ladder, here I assumed that the pivot would be at the point where the ladder touches the floor and again thought that the force by the floor would be parallel to the ladder, but in the figure it showed the force as being closer to the bisector and said something about the force not having to act along the direction of the ladder because the ladder is rigid, which doesn't make it more clear to me.. (link to figure https://ibb.co/DwLJrMW)

I looked at another question in my textbook with this figure (link https://ibb.co/vsr80h5) where they ask for the force by the hinge on the beam and in the figure for the answer it shows the force by the hinge not being along the beam (like I would have assumed, link https://ibb.co/kMZk30K).

So now I'm trying to figure out if my initial reasoning is correct (that the force by the pivot is a reaction force to the weight), and if not, how I can understand where the froce by the pivot originates from/how to identify it.

I checked in my textbook and found an example question about the force by a floor on a ladder, here I assumed that the pivot would be at the point where the ladder touches the floor and again thought that the force by the floor would be parallel to the ladder, but in the figure it showed the force as being closer to the bisector and said something about the force not having to act along the direction of the ladder because the ladder is rigid, which doesn't make it more clear to me.. (link to figure https://ibb.co/DwLJrMW)

I looked at another question in my textbook with this figure (link https://ibb.co/vsr80h5) where they ask for the force by the hinge on the beam and in the figure for the answer it shows the force by the hinge not being along the beam (like I would have assumed, link https://ibb.co/kMZk30K).

So now I'm trying to figure out if my initial reasoning is correct (that the force by the pivot is a reaction force to the weight), and if not, how I can understand where the froce by the pivot originates from/how to identify it.