Importance of Work

The relationship between force and work is an important one to understand.


C2.9 Boy playing tug-of war with dog
Knowing that force is a push or pull on an object, you can predict if the forces are unbalanced or balanced and how that will affect an object. At the start of the lesson, this question was posed: What if I told you that you would have to do no work to hold that weight above your head once it is there? You now know that this is indeed true, because in order for work to be done on the weight, it needs to be moving a distance.

  Virtual Lab

It’s All Uphill © 2017 the Physics Classroom
In this Interactive, you will analyze the motion of a cart being pulled up an inclined plane at a constant speed. The angle of the incline will be modified by 10° increments. In each simulation, the cart is pulled to the same height: 1.0 metre above the original starting position.


To determine the effect of the angle of an inclined plane upon the amount of force and the amount of work done when pulling a cart up an inclined plane at a constant speed and to the same height.

Please click on the procedure tab to continue.
  1. Click on the play button to open the Interactive. This interactive can also be accessed at https://quick.adlc.ca/uphill (There is a small hot spot in the top left corner. Clicking/tapping the hot spot opens the Interactive in full-screen mode. (Use the “Esc” key on a keyboard (or comparable method) to exit from full-screen mode.)
  2. Select the 4.0 kg mass choice. Choose the angle of 30.0°.
  3. Tap the “Run Trial” button. The force required to pull the cart at a constant speed is displayed on the screen; record this in the Data Table.
  4. The displacement (distance) from the starting position to the final position can be measured using the cm scale; record this in the Data Table. (Note that the table lists metres as the unit; 100 cm = 1.00 m.)

    To convert from centimetres to metres, divide the centimetre value by 100.

    For example:

    «math»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«mn»45«/mn»«mo».«/mo»«mn»0«/mn»«mo»§#160;«/mo»«mi»cm«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»?«/mo»«mo»§#160;«/mo»«mi mathvariant=¨normal¨»m«/mi»«/mtd»«/mtr»«mtr»«mtd»«mn»45«/mn»«mo».«/mo»«mn»0«/mn»«mo»§#160;«/mo»«mi»cm«/mi»«mo»§#215;«/mo»«mfenced»«mfrac»«mrow»«mn»1«/mn»«mo»§#160;«/mo»«mi mathvariant=¨normal¨»m«/mi»«/mrow»«mrow»«mn»100«/mn»«mo»§#160;«/mo»«mi»cm«/mi»«/mrow»«/mfrac»«/mfenced»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mn»0«/mn»«mo».«/mo»«mn»45«/mn»«mo»§#160;«/mo»«mi mathvariant=¨normal¨»m«/mi»«/mtd»«/mtr»«/mtable»«/math»

  5.  The force and the displacement directions are both going parallel to the inclined plane. Use the force and displacement to calculate the work done. Remember that W = Fd.
  6. Repeat the procedure for all angles.
  7. Please click on the observations tab to continue.
Angle (°)
Force (N)
Displacement (m)
Work (J)
30.0
40.0
40.0
60.0
70.0
80.0
90.0


Angle (°)
Force (N)
Displacement (m)
Work (J)
30.0
19.6 2.0 39.2
40.0
25.2 1.5 37.8
50.0
30.0 1.3 39.0
60.0
33.9 1.1 37.3
70.0
36.8 1.0 36.8
80.0
38.6 1.0 38.6
90.0
39.2 1.0 39.2

Sample calculation for an angle of 30.0°:

«math»«mn»200«/mn»«mo»§#160;«/mo»«mi»cm«/mi»«mo»§#215;«/mo»«mfenced»«mfrac»«mrow»«mn»1«/mn»«mo»§#160;«/mo»«mi mathvariant=¨normal¨»m«/mi»«/mrow»«mrow»«mn»100«/mn»«mo»§#160;«/mo»«mi»cm«/mi»«/mrow»«/mfrac»«/mfenced»«mo»=«/mo»«mn»2«/mn»«mo».«/mo»«mn»0«/mn»«mo»§#160;«/mo»«mi mathvariant=¨normal¨»m«/mi»«/math»

W = Fd = (19.6N)(2.0 m) = 39.2 J
Please click on the analysis tab to complete the analysis questions.
  1. Describe how varying the incline angle affects the force.

    As the incline angle increases, the amount of force increases.

  2. Describe how varying the incline angle affects the work.

    The incline angle does not seem to have a noticeable effect on the work value.

  3. When a force does work, the object’s energy will change. In this interactive, does the work cause a kinetic energy change or a potential energy change?

    Use this answer for question 10 in Assignment C1.


  Try This

Crossword Puzzle


Download the PDF version and complete the crossword. This crossword will give you practice with the different forms of energy, scientists, and terminology.

Check your work.