![]() ![]() ![]() ![]() The gravitational potential energy U g of a body measures the ability of that body to do work because of its position with respect to another body, usually the earth. A body of mass m moving with speed v (in any direction) has kinetic energy K given by K = 1/2 mv 2. The kinetic energy of a body represents its ability to do work because of its motion. A clear understanding of the definition of each form of energy is a considerable aid in solving energy problems. We have considered three forms of mechanical energy: kinetic energy, gravitational potential energy, and elastic potential energy. ![]() A measure of power that is frequently more useful, however, is in terms of the force F applied to an object moving at a velocity v, that is, P = F ds is negative when the component of F parallel to the displacement of the object is oppositely directed from the displacement.īecause power P is the time rate of doing work, the power developed by a force doing work at any instant is d W/d t, whereas average power P ¯ is the work W done in a time interval Δ t divided by that time interval, or P ¯ = W/Δ t.W a → b = ∫ a b F x d x W a → b = F x ( b − a )Ī common error in computing work results from carelessness with the signs associated with the force applied to an object and the displacement of that object. For this case, the work by a constant force, F = F xî + F yĵ, on an object moving along the x axis is Simpler situations, like the frequently encountered case of a constant force acting on an object that moves in a straight line, say the x axis, are special cases of the general definition of work. The integral in the definition of work suggests that the work done by the force F as the object moves from a to b is equal to the area enclosed by the curve of F s( s), the component of F parallel to ds the s axis and the lines s = a and s = b. Only the component of a force parallel to the displacement of an object can do work on that object. Furthermore, no work is done by F unless there is a component of F along the direction of the displacement of the object. It follows that no work can be done on an object unless the object moves. First, work is done by a force F applied to an object when that object moves from point a to point b. ds, suggests a number of practical facts that are useful in problem-solving. ![]()
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