Lifting a mass from a point that is offset from its center of gravity

In summary, the torque due to the offset will create an arm's length of force, but it won't add to the force needed to lift the mass.
  • #1
Big Tommy C
16
6
TL;DR Summary
Does lifting an object from a point offset from is center of gravity incense force required to lift said object. Does torque that is countered add force required to lift a load?
Good Evening Everyone.

I am having trouble wrapping my head around the physics involved with the example below.
At first i was looking at this as if lifting may create a lever of some sort, but I don't believe it has a fulcrum.
I am trying to find a formula (if there is one) for lifting a mass from a point offset the the center of mass.
Does the force to lift a mass increase with the distance of an offset lifting point such as this in the example below?
I know the offset force will create a torque, assuming the mass is captive in a track of sorts, in this case a roller guide, would it be safe to assume the torque is cancelled out and wont add to the force required to lift this mass?
This is with the assumption that the roller create negligible friction in this example.
Example.png
 
Engineering news on Phys.org
  • #2
Mark the centre of mass on your diagram.
Extend the axis of the force being applied, until it passes the centre of mass.

The torque on the load, due to the offset, will have an arm length equal to the shortest distance between the CofM and the extended axis of the applied force.

You must counter that torque, with say, guide rollers and a vertical rail, in order to avoid increasing the load on the cylinder.
 
  • Like
Likes Big Tommy C
  • #3
Big Tommy C said:
I know the offset force will create a torque, assuming the mass is captive in a track of sorts, in this case a roller guide,
The offset will create a torque even if there are no roller guides. In such a case, the part will accelerate (rotation-wise).
Big Tommy C said:
would it be safe to assume the torque is cancelled out and wont add to the force required to lift this mass?
If some outside torque balances out the torque due to the offset (ex.: coming from roller guides), the mass doesn't accelerate (rotation-wise).
Big Tommy C said:
Does the force to lift a mass increase with the distance of an offset lifting point such as this in the example below?
No. (Assuming friction is negligible and that nothing locks up, i.e. everything stays perfectly straight.)
 
  • Like
Likes Big Tommy C
  • #4
Big Tommy C said:
TL;DR Summary: Does lifting an object from a point offset from is center of gravity incense force required to lift said object. Does torque that is countered add force required to lift a load?

I am having trouble wrapping my head around the physics involved
The key to wrapping your mind around the physics is to create a Free Body Diagram (FBD) (search the term). If you do that for two different length arms, your mind will be wrapped. We will be happy to assist you in doing this.
 
  • Like
Likes Big Tommy C
  • #5
IIRC, a garage or similar work-shop would deploy an adjustable lifting beam, such that 'unbalanced' load is shackled to the ends, but hoisting eye may be moved along beam to balance point by winding threaded rod.

61OGJT6bZ1L._AC_SL1000_.jpg

Due Care, Please ??
 
  • Like
Likes Big Tommy C
  • #6
Big Tommy C said:
Does torque that is countered add force required to lift a load?
Only when the moving parts are not perfectly aligned to be parallel in all planes.
 
  • #7
Big Tommy C said:
I know the offset force will create a torque, assuming the mass is captive in a track of sorts, in this case a roller guide, would it be safe to assume the torque is cancelled out and wont add to the force required to lift this mass?
So long as all the surfaces that the rollers run on are vertical, the roller forces must remain horizontal, so there can be no vertical component of the roller force, that could change the force needed to support, lift or lower the mass.
 
  • #8
Awesome, I understand now. Thanks for the help on this guys!
 
  • Like
Likes Baluncore, Lnewqban and berkeman

Related to Lifting a mass from a point that is offset from its center of gravity

What is the center of gravity?

The center of gravity is the point in a body or system where the entire weight is considered to be concentrated. It is the average location of the weight distribution and is the point where the force of gravity acts on the body.

Why is it challenging to lift a mass from a point offset from its center of gravity?

Lifting a mass from a point offset from its center of gravity is challenging because it creates a torque or rotational force. This torque can cause the object to rotate or tip over, making it difficult to control and requiring additional effort to stabilize the object.

How can you determine the center of gravity of an irregular object?

To determine the center of gravity of an irregular object, you can use the plumb line method. Suspend the object from different points and trace the vertical lines created by the plumb line. The intersection of these lines will indicate the center of gravity. Alternatively, you can use mathematical methods to calculate the center of gravity based on the object's shape and mass distribution.

What techniques can be used to lift a mass safely when the lifting point is offset from the center of gravity?

To lift a mass safely when the lifting point is offset from the center of gravity, you can use techniques such as using counterweights to balance the load, employing lifting aids like cranes or hoists, and ensuring multiple points of contact to distribute the load evenly. Additionally, using proper lifting posture and techniques can help minimize the risk of injury and improve control over the object.

How does lifting a mass from an offset point affect the required lifting force?

Lifting a mass from an offset point increases the required lifting force because it introduces additional torque. To counteract this torque and lift the object without tipping, you need to apply a greater force or use mechanical advantage tools. The farther the lifting point is from the center of gravity, the greater the torque and the more force required to lift and stabilize the object.

Similar threads

Replies
8
Views
2K
Replies
8
Views
465
  • Mechanical Engineering
Replies
10
Views
1K
  • Mechanical Engineering
Replies
5
Views
4K
Replies
13
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
885
  • Introductory Physics Homework Help
Replies
7
Views
369
  • Mechanical Engineering
Replies
2
Views
3K
  • Mechanical Engineering
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
25
Views
1K
Back
Top