How to find the forces acting on the pivot point ?

In summary, to find the forces acting on the pivot point, you will need to first identify all the external forces acting on the object. These can include gravitational force, normal force, frictional force, and applied forces. Next, draw a free body diagram of the object, showing all the forces acting on it and the direction in which they act. Use Newton's second law, F=ma, to calculate the net force acting on the object. Finally, use the principle of torque to determine the net torque acting on the object at the pivot point. This will give you the necessary information to find the forces acting on the pivot point.
  • #1
JJ3
3
0

Homework Statement


pivot point located at the middle of ramp( Point C).
F1=250 lbs @ 12 in from point A
F2=250 lbs @ 84 in from point A
L=192 in
angle from the ground is 25 degrees

Homework Equations


sum of moments equal to 0
sum of forces equal to to 0

The Attempt at a Solution


I did sum of moments about point c equal to 0 , solve for Ra
0=(F1*84)+ (F2*12) - (Ra*96)
Ra= 250 lbs in
Same thing for Rc
0=-(F1*12)-(F2*84)+(Rc*96)
Rc=-250 lbs in
My question is does the angle make a big difference?
 

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  • #2
The reactions are both 250 lbs (not lbs in). The angle makes no difference as long as the symmetry stays the same because all forces are assumed vertical.
 
  • #3
Gordon Mutten said:
The reactions are both 250 lbs (not lbs in). The angle makes no difference as long as the symmetry stays the same because all forces are assumed vertical.
Thank you for the reply.
One more question How would the moment acting on point C affect the pivot pin?
 
  • #4
There are no moment reactions, only force reactions. Therefore the pivot pin is subjected to a vertical shear force only. You can take moments either about point A or Point C because the sum of the moments at these positions is zero.
 
  • #5
Gordon Mutten said:
There are no moment reactions, only force reactions. Therefore the pivot pin is subjected to a vertical shear force only. You can take moments either about point A or Point C because the sum of the moments at these positions is zero.
one last question how would i go about finding the deflection on the beam
 
  • #6
JJ3 said:
one last question how would i go about finding the deflection on the beam
For this you need the E and the I of the beam section. That is the Youngs Modulus of the beam material and the second moment of area that controls bending in the vertical plane. Then I would look up the case of a simply supported beam with a point force in Roark's Formulas for Stress and Strain (Table 3 case 1e in my 5th Edtion). This will give you a formula for the deflection of a beam with one point force. So you need to do the calculation for one point load and then the other and algebraically add the results. I recommend an online tool for doing this as follows: http://www.amesweb.info/StructuralBeamDeflection/SimpleBeamTwoConcentratedLoadsAtAnyPoint.aspx
Treat the beam as if it were level and shorten the lengths by multiplying them by cos(angle).
 

1. What is a pivot point and why is it important to find the forces acting on it?

A pivot point is a fixed point or axis around which an object can rotate or pivot. It is important to find the forces acting on it because these forces determine the stability and movement of the object. Knowing the forces acting on the pivot point can help in predicting the behavior of the object and making necessary adjustments to achieve desired results.

2. How do you determine the forces acting on a pivot point?

To determine the forces acting on a pivot point, you need to first identify all the external forces acting on the object. These forces can include gravity, applied forces, and friction. Next, you need to draw a free body diagram of the object, which shows all the forces acting on the object. Finally, using the principles of equilibrium, you can calculate the net force and torque acting on the object at the pivot point.

3. What is the principle of equilibrium and how is it related to finding the forces on a pivot point?

The principle of equilibrium states that for an object to be in a state of equilibrium, the sum of all the forces acting on it must be zero and the sum of all the torques acting on it must also be zero. This means that the forces acting on the pivot point must be balanced in order for the object to remain in a stable and stationary position.

4. Can the forces acting on a pivot point change over time?

Yes, the forces acting on a pivot point can change over time. This can happen if the external forces acting on the object change or if the object itself moves or rotates, causing a change in the direction or magnitude of the forces. It is important to continuously monitor and adjust the forces acting on the pivot point to maintain stability and achieve desired results.

5. How can the forces acting on a pivot point be manipulated or controlled?

The forces acting on a pivot point can be manipulated or controlled by adjusting the magnitude, direction, or location of the external forces acting on the object. This can be done by adding or removing weights, changing the angle or position of applied forces, or adjusting the surface or environment in which the object is pivoting. Additionally, adjusting the design or structure of the object itself can also affect the forces acting on the pivot point.

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