# Physics definition of work and lifting

My calculus text (Swokowski, Olnikc, Pence, 6th edition) gives the formula for work as $W = Fd$ and then goes on to explain that if the force varies over the distance the formula becomes an integral.

As part of an example, it then shows that the work to lift a 500 lb beam 30 feet would be 500 * 30 = 15,000 ft-lb. But don't we have to exert an upward force greater than the weight of the beam somewhere in our model in order to get the beam to move up? Then the work would be greater than 15,000 ft-lbs according to the definition of work.

It seems that in setting up integrals or just using the formula W = Fd examples always use the weight of the increment or object to be lifted without taking into account the fact that more than that force must be exerted at some point in order for the thing to move upwards.
By the formula W = Fd, if we greatly accelerate an object upwards, the work done lifting the object will be greater than if a lesser acceleration is applied across the same distance, but examples in my book don't seem to take this into account. (I am assuming that F = ma, and of course the mass stays constant.)

• Just so you know what is coming, there definition given here is a 1D restriction of the more general form $\mathrm{d}W = \vec{F} \cdot \mathrm{d}\vec{s}$ where $\mathrm{d}\vec{s}$ is a path element, and the '$\cdot$' represents the dot-product (AKA inner-product or scalar-product) between two vectors. – dmckee Jun 20 '17 at 16:58