Net forces

When two or more forces act on object the motion we see is a result of the net, or vector sum of those forces acting. In this experiment you will use your computer and camera to determine if the net forces sum to zero for a static system.

A static system means that there is no overall motion even though there are forces being applied. Use arrows to annotate the static system illustrated in the images below:

In this experiment you will set up a static system with two spring balances and brass weights and two retort stands as shown below. Annotate the diagram with arrows to show the forces.

You will then use vector analysis to show that all the vectors sum to zero. In vector addition, vectors are placed ‘head to tail’ and then the resultant is drawn from the starting ‘tail’ to the ‘final’ head. Did you expect to get a resultant in a static situation? Explain

Method

• Set up your equipment and take a photo of the static system

• Take accurate readings of the two spring balances

• Calculate the weight force using W=mg, remember mass must be in kg and take g = 9.8 m/s²

• Copy your image to a word doc.

• Use a scale of 1cm = 1 N

Draw scaled arrows over your photo and match them up to the angles of the spring balances.

Then make copies of the arrows and attempt to join them as vectors. If you have been accurate the vectors should join perfectly into a triangle.

Repeat this for two more different variations in angles of the spring balances.

Did your vectors make a closed shape (or close to a closed shape) each time?

What is the resultant vector for each test?

What are the sources of error in this activity?

What can you conclude from your data?

Watch this video on how to use word to draw vectors on your image

Watch this video to see how to add your vectors using word