From Force to Work
So here's an interesting question for you, if you are pushing on a brick wall with all your might, sweating and panting and shoving, wearing out your muscles until you are trembling all over.... is that hard work?
I'm betting most of you would say yes, that looks like a lot of hard work. The problem is work has a different definition when we use it in an every day kind of way than the definition it has in science. When we use it in an every day way, we mean doing anything that makes us very tired or that takes a lot of time and effort to do. In science things are a little different.
The above formula shows how we calculate work in science. In order for work to be done, you have to have two things:
1. A force has to be applied to an object
2. That object has to move some amount of distance.
So, go back and look at the comic above. The little man (lets call him Bob) is pushing on that wall with all of his might, putting a lot of effort into it. Let's say Bob can muster up 100N of force to put on that wall. He has achieved the first requirement of work, putting a force on an object. However, that wall is determined to stay where it is, no matter how hard the poor little Bob pushes. That wall isn't going anywhere. So, since no distance is being covered, no work is being done, in science terms at least. Lets look at it in equation form:
1. A force has to be applied to an object
2. That object has to move some amount of distance.
So, go back and look at the comic above. The little man (lets call him Bob) is pushing on that wall with all of his might, putting a lot of effort into it. Let's say Bob can muster up 100N of force to put on that wall. He has achieved the first requirement of work, putting a force on an object. However, that wall is determined to stay where it is, no matter how hard the poor little Bob pushes. That wall isn't going anywhere. So, since no distance is being covered, no work is being done, in science terms at least. Lets look at it in equation form:
![Picture](/uploads/2/0/1/1/20114429/work-equation-2.png?250)
We can start with just the equation, that work equals a force multiplied by the distance traveled.
Then, we plug in that Bob is putting 100 Newtons of force on the wall and that the wall has moved 0 meters since Bob started pushing it.
Unfortunately for Bob, when we actually multiply that, anything multiplied by 0 is still 0, so we end up with 0 Joules. Oh yeah! Joules is the unit we assign to work, so any time you see Joules, you will know that the problem had to do with work.
Then, we plug in that Bob is putting 100 Newtons of force on the wall and that the wall has moved 0 meters since Bob started pushing it.
Unfortunately for Bob, when we actually multiply that, anything multiplied by 0 is still 0, so we end up with 0 Joules. Oh yeah! Joules is the unit we assign to work, so any time you see Joules, you will know that the problem had to do with work.
Well, now lets give Bob another try. We know he isn't slacking off, he just ended up pushing on the wrong object, right?
![Picture](/uploads/2/0/1/1/20114429/editor/work-2.jpg?1491418619)
Here we can see that Bob is carrying a very heavy backpack to school with him. Lets say that, in order to lift and carry that backpack, it takes 20 Newtons worth of force. So Bob has once again fulfilled the first requirement of doing work, putting a force on an object.
Bob walked to school every morning carrying that backpack. Lets say he has to walk 1000 meters from his front doorstep to the schoolroom, where he can set his bag down. Bob would then fulfill the second requirement of doing work, moving the object some distance.
Just to recap, this means that Bob used 20 Newtons worth of force to move his backpack 1000 meters to school every day. Now we can figure out just how much work Bob is doing.
Give it a try. When you think you have your answer, click the button to go to the next picture and check your answer.
Bob walked to school every morning carrying that backpack. Lets say he has to walk 1000 meters from his front doorstep to the schoolroom, where he can set his bag down. Bob would then fulfill the second requirement of doing work, moving the object some distance.
Just to recap, this means that Bob used 20 Newtons worth of force to move his backpack 1000 meters to school every day. Now we can figure out just how much work Bob is doing.
Give it a try. When you think you have your answer, click the button to go to the next picture and check your answer.
Great! So Bob does 20,000J of work every day just walking to school. He must to the same amount going home! Thats a lot of work for poor Bob! I guess he is not so lazy after all...