# What forces are exerted on a pivot and its support in a see-saw lever?

• yhawke
In summary, the conversation discusses a see-saw type lever and the forces exerted by its components. The first question asks about the force exerted by the blue bar on the red support, with a guess of 1N to the left. The second question is about the force exerted down on the pivot, with a guess of 3N straight down. The conversation also mentions the use of torque and Newton's laws to calculate these forces.
yhawke
Hi there,
I have a two part question, just for my understanding not homework. Say you had a see-saw type lever like in my attachment. The yellow ball represents a 1N force and the green 2N and they are both 1m from the pivot. The blue bar is a beam attached hanging down directly off the lever so that it keeps the lever perfectly horizontal. My questions are:

1. What force does the blue bar exert on the red support? (My guess is 1N to the left.)
I think I'm confusing myself because it's directly under the pivot and therefore I'm thinking it has no torque, but surely it is exerting a force?

2. What force is exerted down on the pivot? (My guess is 3N straight down.)
But my thinking is maybe the red support is taking some of the load off the pivot so maybe less than 3N?

Any help is appreciated, I'm an absolute novice trying to teach myself with an old textbook.

#### Attachments

• pivot.bmp
229.6 KB · Views: 1,182
got 1) you should know how to play with torque :)

its obvious that the blue and red bar will meet at a point (ad not a surface) ... calculate the distance of this point from the pivot ... the force due to this contact provides restoring torque such that it balances the torques due to the 2 balls.

2) help coming up

EDIT:
2)
for this just use simple Newton's laws ...
upward force due to pivot balances the plank and the yellow and green ball's weights.

## 1. What is a pivot and how does it work?

A pivot is a point or axis around which an object can rotate. It typically consists of a support and a fulcrum, which is the point where the object is supported and can rotate. The pivot allows for the application of force to cause rotational motion.

## 2. How does force act on a pivot?

Force acts on a pivot by causing a rotational motion around the fulcrum. The direction and magnitude of the force will determine the direction and speed of the rotation. The force must be applied at a distance from the fulcrum to create a torque, or turning force.

## 3. What factors affect the force acting on a pivot?

The force acting on a pivot is affected by the magnitude and direction of the force, the distance from the fulcrum, and the mass and distribution of mass of the object being rotated. The force applied must also be greater than the resisting force to cause rotation.

## 4. How is the force acting on a pivot calculated?

The force acting on a pivot can be calculated using the equation F = r x m x a, where F is the force, r is the distance from the fulcrum, m is the mass of the object, and a is the acceleration of the object. This calculation takes into account the torque, or turning force, needed to cause rotational motion around the pivot.

## 5. What are some real-world applications of force acting on a pivot?

Force acting on a pivot is used in various real-world applications, such as seesaws, crowbars, and scissors. It is also used in engineering and construction, such as in the design of levers and other mechanical systems. In addition, it is an important concept in physics and can be observed in the motion of planets and other celestial bodies.

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