19
Vector Addition Lab
Objective:
To confirm experimentally that forces obey the laws of vector addition and to practice the
techniques involved with vector addition and subtraction, both algebraically and graphically.
Procedure:
1. Level the force table. Then attach the following masses to the ring on the force table. Don't
forget to include the mass of the hanger. Notice that the ring is NOT in equilibrium under the
action of the three forces alone. If you removed the peg (which applies a force to the ring), the
ring would accelerate.
200 grams at an angle of 0.0 degrees.....This provides force .
100 grams at an angle of 70.0 degrees....This provides force
.
150 grams at an angle of 150.0 degrees...This provides force .
Convert all three masses to weights in newtons for use in the calculations below. Keep in mind
that the magnitudes of these forces are always in newtons, not grams or kilograms.
2. Graphically construct the sum
to scale on a piece of paper using the tip to tail
method. That is, draw to scale. Choose a scale of 3.50 cm = 1.00 N. Then, using the tip to tail
method add
to (also drawn to scale). Then add to
. Finally, draw a vector from the
tail of to the tip of and call it
for resultant. Measure the length of
with a ruler in cm, and
convert it to N (newtons). Also, measure the angle in degrees that
makes with the positive x
axis using a protractor. Write down these numbers (magnitude of
in N and the angle it makes
with the positive x axis) on the diagram and enclose them clearly in a box.
As an example, let's say you have two vectors, and
, as shown below.
There are coordinate axes with each vector to help you visualize the angles associated with them.
Note that the x- and y-axes point in the same directions for both vectors. Once you assign the
directions of the x- and y-axes, those must remain consistent throughout the problem. You are
allowed to move vectors around by repositioning the beginning (the tail) of each vector, but you
cannot change the rotation of the axes, or the direction that the vector points. Note that the angle
of each vector, θG and θH, are both measured from the positive x-axis.
