Does Gravity Affect the Inertia Load in a Dual-Weight Pulley System?

[CuriousAbout]

I have a counterweight system I am trying to develop. One of my associates and I are in disagreement over something though.

The system is simple, it is effectivly two 850 Lb weights connected together by a chain. The chain is suspended by two pulleys. One of the pulleys is connected to motor. I am trying to calculate the torque required to move the system 40 inches in 1 second.

I believe the only forces that I have to overcome is inertia due to acceleration and the system friction. Assuming there is no friction the inertia is all that is l have to overcome.

Here is my question: Is the inertia load 1700 Lbs or 850. My associate says gravity will remove one of the loads but if gravity acts on both weights shouldn't it cancel out?

 

[Meir Achuz]

You are correct.

 

[astrokreng]

I would like to clarify that inertia is not a force, but rather a property of matter that describes its resistance to change in motion. In this scenario, the inertia of the weights will play a role in the acceleration of the system, but it is not a force that needs to be overcome.

To calculate the torque required to move the system, we need to consider the forces acting on the weights. In this case, there are two forces acting on each weight: the force of gravity pulling them downward and the force of the chain pulling them upward. These forces are equal in magnitude, but opposite in direction, resulting in a net force of zero and no movement.

However, when the motor is turned on, it will apply a torque to the pulley, causing the chain to move and the weights to accelerate. The amount of torque required will depend on the mass of the weights and the acceleration you want to achieve. It is not correct to assume that the inertia of the weights is the only force that needs to be overcome.

In terms of the question about the inertia load, it is not accurate to say that it is either 1700 lbs or 850 lbs. The inertia of the system will depend on the mass and distribution of the weights, as well as the acceleration. It is important to consider the mass of both weights when calculating the torque required.

In conclusion, the torque required to move the system will depend on the forces acting on the weights, including gravity and the force applied by the motor. The inertia of the system will play a role in the acceleration, but it is not a force that needs to be overcome. It is important to consider all forces and factors when designing your counterweight system.