Physics Experiment
Forces & Equilibrium
BHS
-> Staff
-> Mr. Stanbrough ->
Physics -> Mechanics
-> Newton's Laws ->
Newton's First Law -> this
page
Question:
When an object is in equilibrium, what can you say about the
forces that are pushing and pulling on it?
Equipment:
force table
|
2 spring scales
|
graph paper
|
washers
|
Procedure
Part 1 - Forces in One Dimension
- Tie a loop in both ends of a short piece of string.
- Calibrate (adjust the scale) your spring scales so that they
both read the same force when they support the same object.
- Put a loop over each spring scale hook, and have a person pull
on each spring scale. The string should remain at rest, or move at
constant velocity, while the people pull on it.
- In a data table, record the force on each spring scale.
- In order to get an idea of the precision of your measurements,
check to see how much one person can vary their spring scale
reading without affecting the reading on the other scale. Record
this information.
- Repeat for a few other "pulls".
Part 2 - Forces in Two Dimensions
- Your teacher will show you how to set up the force table
apparatus so that 3 forces are pulling on the central ring.
- Adjust two of the forces so that they are directed at
0o and 90o respectively. The direction of
the third force will vary, depending on the number of washers you
place on the weight hangers.
- Adjust the direction of the third (non-perpendicular) force
(by moving the string), and the amount of each force (by changing
the number of hanging washers) until the central ring does not
touch the post.
- Record the magnitude of each force (number of washers) and
direction of each force in a data table.
- In order to test the precision of your measurements, check to
see about how much you can move a string, or change the number of
washers, without disturbing the central ring.
- Repeat the procedure so that each person in your group has at
least one experimental trial to analyze.
Results:
Part 2 - Forces in Two Dimensions
For each set of forces:
- Determine the resultant (magnitude and direction) of the two
vectors at 0o and 90o - you many use either
algebra and trigonometry or a scale drawing.
- Make a scale drawing showing your resultant vector from step 1
and the third vector in the set. Draw the vectors with their
"tails" together.
Conclusions:
Part 1 - Forces in One Dimension
How do the forces on the 2 spring scales compare? In particular,
given the variation that you noted in step 5 above, could the two
forces be equal in size?
Part 2 - Forces in Two Dimensions
For each set of vectors, how does the third vector in each set
compare with the resultant of the other two vectors? What does this
tell you about the net force on the ring? Why?
BHS
-> Staff
-> Mr. Stanbrough ->
Physics -> Mechanics
-> Newton's Laws ->
Newton's First Law -> this page
last update November 10, 2007 by JL
Stanbrough