Solving a Lever Problem: Need Help from Experts | Join Our Forum!

  • Thread starter Girn
  • Start date
  • Tags
    Lever
In summary, the mathematician was trying to solve a problem involving two supports and a beam, but wasn't able to get an answer because of a mistake in the calculation.
Physics news on Phys.org
  • #2
Summarizing the problem in text avoids making people squint at photographs.

33m beam has two supports
overhangs both by 5m
600kN at extreme right end
900kN at extreme left end
159kN/m over entire length
Calculate support reactions.
...

You seem to have worked the torques...
Where did you get stuck? Work slowly through the math - showing your reasoning.
 
  • #3
I don't know where I am getting stuck, but I aint getting the answer. I am not sure what I am doing wrong.. I've tried so many different combinations.. obviously the basis for the formula is clockwise movements=counterclockwise movements, but I aint getting the answer.. and 900kN is not at the extreme left end, its 8m from the left end.
 
  • #4
Oh I misread that - see the problem with presenting the problem in a photograph?

I'm having trouble treading your working in the photo - I see a 900x8 in there ... that would be the torque about the extreme left end from the 900kN point force. But there is no pivot there: the pivot is 5m, in from that end.

You can reality check your answer by noticing that the total downward force has to equal the total upward force (the beam ain't going anywhere.)

Mind you - taking a look at the answers they give (3297kN and 3453kN) I see they add up to 6750kN upwards... the total downwards force is 6747kN, suggesting that the beam will lift off under a net unbalance 3kN.

I think the distributed force was supposed to be 159.09kN/m ... and somebody rounded off when they shouldn't have.
 
  • #5


Hi there! I'm glad you joined our forum for help. Lever problems can be tricky, but don't worry, we can figure this out together. First, let's start by understanding the problem. The picture shows a lever with three weights on one side and two weights on the other side. The goal is to find the weight of the unknown object on the right side.

To solve this problem, we can use the principle of moments. This states that the sum of the moments on one side of the lever is equal to the sum of the moments on the other side.

In this case, we have three known weights on the left side, and one known weight and one unknown weight on the right side. Using the principle of moments, we can set up the equation:

(5kg x 10cm) + (3kg x 20cm) + (2kg x 30cm) = (4kg x 40cm) + (xkg x 50cm)

Simplifying this equation, we get:

50kgcm + 60kgcm + 60kgcm = 160kgcm + 50x

170kgcm = 160kgcm + 50x

10kgcm = 50x

x = 0.2kg

Therefore, the weight of the unknown object on the right side is 0.2kg.

I hope this helps! If you have any further questions or need clarification, don't hesitate to ask on the forum. We are here to help and support each other in our scientific endeavors. Keep up the good work!
 

1. What is a lever?

A lever is a simple machine consisting of a rigid bar or plank that pivots around a fixed point, called a fulcrum. It is used to amplify or redirect a force, making it easier to lift or move heavy objects.

2. How does a lever work?

A lever works by using the principle of mechanical advantage, which states that the effort required to move an object can be reduced by increasing the distance from the fulcrum to the point where the force is applied. This allows for the same amount of work to be done with less force.

3. What are the three classes of levers?

The three classes of levers are determined by the relative positions of the fulcrum, effort, and load. In a first-class lever, the fulcrum is located between the effort and load. In second-class levers, the load is between the fulcrum and effort. In third-class levers, the effort is between the fulcrum and load.

4. How does the length of the lever affect its performance?

The longer the lever, the greater the mechanical advantage and the easier it is to move heavy objects. However, a longer lever also requires more space and may be more difficult to operate in certain situations. The length of the lever should be chosen based on the specific task at hand.

5. What are some real-life examples of levers?

There are many real-life examples of levers, including seesaws, scissors, pliers, crowbars, and wheelbarrows. Levers are also used in everyday objects such as door handles, bottle openers, and light switches. The human body also utilizes levers, such as the bones and muscles in our arms and legs, to perform movements and tasks.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
10
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
3K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
8
Views
12K
  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
9
Views
13K
  • Introductory Physics Homework Help
Replies
1
Views
4K
Back
Top