Sam Peppiatt wrote: ↑Tue Dec 05, 2023 12:43 am Tarsier,
I was referring to shifting weights in & out on a radius. But no matter, either way it doesn't work. however , if a scientist says it's because of minor losses due to friction; I say he doesn't have a clue----------------------Sam
Imagine a pendulum bob on a string , it falls from 12 and reaches about 11 , this is already a singular demonstration of losses of which one example is the bob colliding with air molecules and the larger the surface of the bob the more air molecules collide with it (air drag / resistance ) because air has mass (think of a tub filled with balls as the air molecules and the pendulum bob swings through it) , a kite being pushed up with the wind or a windmill turning is already an example of the air's ability as a force and mass.If a weight is fixed to a wheel and you let it go it will get back up to about eleven and no more. That's the zero or less sum game, right? And, I agree it lacks the energy to get all the way back to 12. However, if I try to shift a weight out on the down side and back in on the up side, I'm lucky to get back to 8.
Imagine your car stranded by the side of the road which is a flat horizontal surface, you have to push it out of the road and the push across the distance it has to move takes work , the work is the force you have to apply times the total distance you have to apply that force across ,to do that work you have to transfer energy , if you have no energy you cant push it (imagine running a mile and trying to then push a vehicle) but if you have energy you can push it .
The car has mass and the larger the mass the larger the inertia , inertia is just how much something resists change , so the more mass or inertia an object has the harder it is to get it to change direction or start moving .
Imagine your pendulum's ability to reaching 11 o' clock , as a car being able to travel 11 miles/km on its fuel , but by taking extra trips to other places it burns off fuel , which means less fuel is less distance it can travel in the end it only reaches 8 miles/km.
With this in mind as an example of the pendulum having energy losses , if the pendulum goes out on the downside and in on the upside , these in and outwards motion costs energy usage (like you needing energy to push the heavy car or the fuel being burned by extra trips) , and the only energy you have available is that from the falling weight , when that weight is being forcefully moved it costs energy which would be subtracted from the total energy it had (when you pushed the car you burned energy or when the car travels extra trips it burns fuel) , before it would reach 11 o clock and now it would reach for example lets say about 8 o clock as your given example , if you run a mile and then push a vehicle you cant push very far because you don't have enough energy but if you did not run a mile and then push the vehicle you can push it further , or if the car has not burned off fuel from extra trips it could reach 11 miles/km instead of 8 miles/km.
There are also many ways that energy is lost in a mechanical system apart from air resistance and friction too , all the losses and expenditure of energy adds up .