The discussion revolves around the hypothetical scenario of whether a feather could lift a car using a lever system. Participants explore the feasibility of this idea from both theoretical and practical perspectives, considering factors such as mechanical advantage, friction, and the design of the lever system.
Participants generally agree that while the concept is theoretically interesting, practical limitations and the complexities of mechanical systems create significant challenges. There are multiple competing views on the specifics of how friction and mechanical advantage play into the feasibility of the scenario.
Participants express uncertainty regarding the efficiency of mechanical systems, particularly in relation to load and friction. The discussion does not resolve these uncertainties, and assumptions about ideal conditions versus real-world applications remain unaddressed.
In an ideal situation, yes but in reality no. You would need a MASSIVELY leveraged system and in any real such system, there would be friction and losses that would utterly swamp the weight of a feather.CharlohAwk said:I'm no physics major... And I have no formal education... I just have a task that I wonder if could be possible... Could a feather lift a car? Could you use the weight of a feather and the proper lever system or systems to lift a standard sized car off the ground?
While each stage of a multi-stage lever/gear/pulley/whatever system will drain a fraction of the input power due to frictional losses, the output never becomes non-zero. The losses are multiplicative, not additive.phinds said:In an ideal situation, yes but in reality no. You would need a MASSIVELY leveraged system and in any real such system, there would be friction and losses that would utterly swamp the weight of a feather.
I've been away from classical mechanics of this sort for so many decades that I totally forgot that (if I ever knew it in the first place). It seems counter-intuitive but I'll take your word for it.jbriggs444 said:The losses are multiplicative, not additive.
It is not something that they explicitly teach in school. It is what I would consider an obvious consequence. Power out = power in times efficiency. If you want the efficiency of a chain of devices, you take the product of the efficiencies at each step in the chain.phinds said:I've been away from classical mechanics of this sort for so many decades that I totally forgot that (if I ever knew it in the first place). It seems counter-intuitive but I'll take your word for it.
Sure, so?DrClaude said:Don't you need to first overcome static friction?
Sounds fair to me. Make sure the lever is balanced by itself before you put the car and feather on. However...joel59 said:In a windless environment with precisly the right size lever and fulcrum it seems the added weight on the lever should work - a tipping point. Maybe this is cheating since the extremely long lever weights the action.
Isn't that only in the case of a linear system?jbriggs444 said:The losses are multiplicative, not additive.
You are correct. The friction-based loss model that I have in mind is one that is approximately linear over the expected operating conditions.sophiecentaur said:Isn't that only in the case of a linear system?
Sure. But MA is roughly independent of load under the expected operating conditions for devices with a fixed gear ratio.Efficiency is Mechanical Advantage / Velocity Ratio and the MA is not independent of load.