best rolling school bags image
cenalover3
i have the michael jackson bag and i refuse to use it because i dont want to mess it up...i see alot of girls at school with those bags so i was wondering how long are these bags are going be in style?
Answer
To be honest i don't know what they are, i live in australia and have no clue about them, but i do have the rolling stone magazine and the front cover is adddddoorrrable, here it is...
To be honest i don't know what they are, i live in australia and have no clue about them, but i do have the rolling stone magazine and the front cover is adddddoorrrable, here it is...
does it require energy to maintain a state of potential energy?
Maanav G
when i hold my sons school bag up it requires energy not only to lift it but even to keep it up.
according to the law of conservation of energy, energy cannot be created nor destroyed.
then where is this energy going????
is the energy getting used up in just maintaining a state of potential energy????
Answer
You are combining two different concepts in your example.
Your original question on whether energy is required to maintain a state of potential energy would be better observed if you hang the school bag on a doorknob or a coat hook. The potential energy stored in the elevation of the bag against gravity remains, but there is no energy being consumed to maintain that position.
In a biological system where the skeleton is not locked, but is relying on muscle activity to maintain position, the muscle fibres are continuously being stretched by the weight of the bag, and contracted by the firing of neurons. Energy is being consumed by the muscles to maintain their contracted state and this energy is being expressed mostly as heat, which is why we sweat when we are lifting weights.
So when you hold your son's school bag off the floor, energy is consumed by your body in maintaining that position, but none of it is transferred to the bag, and the potential energy stored in the bag is not altered.
Another example of energy being consumed to maintain potential energy is when we stop a car part way up a hill. If the car has a manual transmission, then we can maintain our position by revving the engine and slipping the clutch just enough to keep from rolling backwards. As long as the car is not rolling backwards or advancing, the potential energy remains unchanged. The energy of the engine is being expressed as heat through the clutch, and the force of friction created by the slipping clutch is maintaining the potential energy. Note this is a force, not energy.
You are combining two different concepts in your example.
Your original question on whether energy is required to maintain a state of potential energy would be better observed if you hang the school bag on a doorknob or a coat hook. The potential energy stored in the elevation of the bag against gravity remains, but there is no energy being consumed to maintain that position.
In a biological system where the skeleton is not locked, but is relying on muscle activity to maintain position, the muscle fibres are continuously being stretched by the weight of the bag, and contracted by the firing of neurons. Energy is being consumed by the muscles to maintain their contracted state and this energy is being expressed mostly as heat, which is why we sweat when we are lifting weights.
So when you hold your son's school bag off the floor, energy is consumed by your body in maintaining that position, but none of it is transferred to the bag, and the potential energy stored in the bag is not altered.
Another example of energy being consumed to maintain potential energy is when we stop a car part way up a hill. If the car has a manual transmission, then we can maintain our position by revving the engine and slipping the clutch just enough to keep from rolling backwards. As long as the car is not rolling backwards or advancing, the potential energy remains unchanged. The energy of the engine is being expressed as heat through the clutch, and the force of friction created by the slipping clutch is maintaining the potential energy. Note this is a force, not energy.
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