Exploring the Relationship between Work and Constant Velocity

[CollinsArg]

Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume this? (e

 

[NFuller]

Should I always assume this?

No, you may find cases where the velocity is not constant. In these cases the work is defined using an integral expression:
$$W(t)=\int_{0}^{t}\mathbf{F}\cdot\mathbf{v}(t')dt'$$
I'm not sure if you are familiar with calculus though.

 

[jbriggs444]

Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume this? (e

It is usually a simplifying assumption written into first year physics problems.

Say, for instance that you are pushing a wagon up a hill. The problem asks how much work you have done pushing the wagon up the slope. But the author wants you to be thinking of gravitational potential energy (mgh). The author does not want you distracted worrying about pushing too hard and winding up with a rapidly moving wagon at the top. Or not pushing hard enough and having the wagon starting with high speed and coasting to a stop at the top with no work done.

So the author either may write that the wagon is pushed at a constant velocity or that the wagon is pushed slowly.

It is perfectly valid to consider the work done pushing a wagon with frictionless wheels on a level road. Naturally such a wagon will speed up as you go. The work done is still valid and will then correspond to the difference between the wagon's starting and ending kinetic energy.

 

[CollinsArg]

Thank you :)