Efficiency of Ramp Pulling: Friction vs. No Friction

AI Thread Summary
In the discussion on ramp pulling efficiency, it is suggested that pulling a cart up a frictionless ramp may yield lower efficiency compared to a ramp with friction. The participant struggles to calculate the effort force, noting that with no friction and constant speed, the effort force should equal the gravitational force acting on the cart. It is clarified that in a frictionless scenario, the work done by the pulling force matches the work done against gravity. The conversation emphasizes the importance of understanding the relationship between work, forces, and efficiency in different scenarios. Ultimately, the nuances of work-energy principles are critical for accurately determining efficiency in these cases.
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Homework Statement


In an ideal case of pulling a cart up a ramp where there is no friction should the efficiency be less than that of pulling a cart up a ramp with friction?

Homework Equations


W=F\DeltaXcos\theta
Efficiency=(work output/work input)*100

The Attempt at a Solution


I was trying to calculate this for a lab and my efficiency came out to be much less for a friction-less ramp than one with friction. Is this possibly right?
What I believe one of my problems was, was determining the effort force. How do you determine the effort force if you only know that there is no acceleration, no friction, the length of the ramp is 1.22 m and the mass of the cart is 0.783 kg?
 
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Let's say you pull a cart up an incline at constant speed.

If there is no friction, then all the work your muscles do matches the negative work done by gravity and nothing else.

If there is friction, then the work that your muscles do matches the negative work done by gravity and the negative work done by friction.

The effort force is the sum of all the other forces when the object is moving at constant speed. This is a consequence of the work energy energy theorem.
 
So if there is no friction and the force of gravity is say 8 N, then the effort force is 8 N?
 
I didn't say the forces are equal. If there is no friction, the work done by gravity is equal to the work done by the pulling force. The forces will be equal only if the cart is pulled vertically up. Use the definition for work to see why this is so.
 
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