Lesson 1.5: Calculating Work

You now know what work is.  Now, apply the knowledge and the formula for work to calculate how much work is done.

Calculating work done using the work formula requires that force and distance be given.

Example:
A student exerts a force of 500 newtons to lift some books from the floor to the top of a desk that is 1.2 m high.  How much work did the student do?

Answer:
Use the formula W = F*d (Work = Force x distance), and substitute the values for force and distance.

W = F*d
W = (500 N)(1.2 m)
W = 600 N·m  = 600 J

Now, try some practice questions.

Question 1. How much work would you do if you carry a 1000 N box up some stairs to a total height of 7 m?

Question 2. How much work would you do if you hold a 1000 N box and take the elevator up a total height of 7 m?

Question 3. How much work would you do if you apply a 400 N force pushing a car a total distance of 100 m?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. How much work would you do if you carry a 1000 N box up some stairs a total height of 7 m?

W = F*d
W = (1000 N)(7 m)
W = 7000 N·m  = 7000 J

Question 2. How much work would you do if you hold a 1000 N box and take the elevator up a total height of 7 m?

You would not be doing any work.  The elevator would be doing the work.  Just holding the box does not constitute work.

Question 3. How much work would you do if you apply a 400 N force pushing a car a total distance of 100 m?

W = F*d
W = (400 N)(100 m)
W = 40 000 N·m  = 40 000 J

 


Now, do assignment 7A.  Page forward to access the computer-scored assignment.