- #1
Desiderus
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Hello all. I'm having trouble understanding why exactly it is that the simple work formula is defined both as change in energy and force times distance, and I'm hoping that it can be made clear to me.
Allow me to clarify. In physics, the word work has two definitions. The first, what I call the "conceptual definition", is a measure of change in energy of an object over a distance with a force acting constantly on an object. The second, what I call the "mathemetical definition", is :
W = F x d
with "W" being work in joules
"F" being Force in Newtons
and "d" being distance in meters
My problem lies in reconciling these two definitions. To me, they seem inconsistent. A force necessarily involves acceleration, which means non-linear (parabolic) increases in distance with respect to time. This, of course, means that work, being a product of what we shall assume is a constant force and a non-linear distance, is also non-linear with respect to time.
Now, if energy is being applied through a force of constant magnitude, and we are to assume that the object is indeed moving and the force is indeed parallel to the object being acted upon, why is it that, per the work formula, energy does not flow into an object at a constant (linear) rate with respect to time? If a force is measured in Newtons, and thus kilogram meters per second per second, then isn't a certain amount of energy flowing into the object per second (per any time interval, for that matter)? And isn't it the same amount of energy being transferred from second to second (or time interval to time interval, so long as the time intervals being compared are the same length)? Clearly not, though I cannot for the life of me see why. I have been laboring under what is perhaps the delusion that the magnitude of a force in Newtons describes how much energy the force in question is applying per second.
If the work formula were instead the momentum formula (p = m x v) this would make perfect sense to me. A certain speed times a certain mass yields a certain energy. If, force example, a certain amount of energy would make an object of one kilogram move at a rate of 10 meters per second, it would seem very natural to me that the same amount of energy would move an object of two kilograms at a rate of 5 meters per second. Energy proportional to both mass and velocity seems perfectly sensical, so where do we get all this stuff about force times distances and (1/2)mv^2?
Allow me to clarify. In physics, the word work has two definitions. The first, what I call the "conceptual definition", is a measure of change in energy of an object over a distance with a force acting constantly on an object. The second, what I call the "mathemetical definition", is :
W = F x d
with "W" being work in joules
"F" being Force in Newtons
and "d" being distance in meters
My problem lies in reconciling these two definitions. To me, they seem inconsistent. A force necessarily involves acceleration, which means non-linear (parabolic) increases in distance with respect to time. This, of course, means that work, being a product of what we shall assume is a constant force and a non-linear distance, is also non-linear with respect to time.
Now, if energy is being applied through a force of constant magnitude, and we are to assume that the object is indeed moving and the force is indeed parallel to the object being acted upon, why is it that, per the work formula, energy does not flow into an object at a constant (linear) rate with respect to time? If a force is measured in Newtons, and thus kilogram meters per second per second, then isn't a certain amount of energy flowing into the object per second (per any time interval, for that matter)? And isn't it the same amount of energy being transferred from second to second (or time interval to time interval, so long as the time intervals being compared are the same length)? Clearly not, though I cannot for the life of me see why. I have been laboring under what is perhaps the delusion that the magnitude of a force in Newtons describes how much energy the force in question is applying per second.
If the work formula were instead the momentum formula (p = m x v) this would make perfect sense to me. A certain speed times a certain mass yields a certain energy. If, force example, a certain amount of energy would make an object of one kilogram move at a rate of 10 meters per second, it would seem very natural to me that the same amount of energy would move an object of two kilograms at a rate of 5 meters per second. Energy proportional to both mass and velocity seems perfectly sensical, so where do we get all this stuff about force times distances and (1/2)mv^2?