Allan Hancock College

Allan Hancock College

Physics Lab

Vectors

Purpose: The purpose of this lab is to practice vector addition using force vectors.

If we have 2 vectors, A and B, which can be written as

then the sum of A and B is a resultant vector R,

Rx = Ax + Bx and Ry = Ay + By.

Finally the magnitude of R is

and the direction of R is given by the angle q,

q = tan-1(Ry/Rx).

Apparatus: Force table, weights, strings, graph paper, and protractor.

Procedure:

Exp. 1: Adding 2 vectors to determine the resultant vector (net force).

Using the force table with one pulley at 0o and another at 90o, apply 2 forces to center ring by hanging different masses over the pulleys.

Find the magnitude of each weight force by using

weight (w) = mg.

Use g ~ 10 m/s2.

Draw an accurate vector diagram of the forces. Add them together using vector addition and trigonometry to find magnitude and direction of the net force (resultant vector). Draw the resultant vector on your diagram, and measure its length and the angle. How does it compare with your theoretical prediction?

Using this information, predict the magnitude and direction of a 3rd force that would make the net force on the ring equal to 0. Try it!

Experiment 2: Adding x and y components.

Apply a single force in a direction between 0o and 90o and find its x and y components. What 2 forces should be applied to the –x and –y directions to balance these components? Test your prediction.

Repeat for a different initial force vector.

Experiment 3: Adding 3 vectors.

Balance the ring experimentally with 3 force vectors.

Determine the magnitudes and directions of all the forces, resolve them into x and y components, and add them to find the net force. The net force should be approximately 0.0N. What do you find?

Repeat this with 4 force vectors.

Experiment 4: Vector addition.

Apply 2 or more forces in any directions, but not at 0o and 90o or any other right angle configuration. Now calculate the net force. Predict the additional force (magnitude and direction) needed to balance this net force. Test your prediction.