Experiment to determine the mass of an unknown object by vector analysis.

Apparatus

Spring balance, string, protractor, retort stand, 2 small-wood blocks and unknown mass (m).

Method

a) Set up the apparatus as shown in figure below

b) Pull the spring balance horizontally until θ = 10° or 40°c) Record the spring balance reading (F x) in a suitable tabled) Repeat for θ = 10°, 20°, 30°, 40° or 40°, 50°, 60°, 70° depending on the capacity of your spring

balance. For a capacity of 100 grams use angles θ = 10°, 20°, 30°, 40°. For a spring capacity of 1 kilogram use θ = 40°, 50°, 60°, 70°.

e) Draw a free body diagram of the system.

Calculate the unknown mass for each θ by the equation m=F x

g× tan (θ)

f) Plot F x vs. tan (θ) in a suitable graph (Include: Title, scale of x and y axis, x and y axis unit labels, a curve-fit line and data points. Take advantage that there are 5 minor blocks per major line. Use the largest portion of the paper as you can when choosing a scale. Data points should be marked by a small x and a small circle.

Questions

1. What is the graphical relationship between F x vs. tan (θ). Can you quantify this relationship? If you can, what is it?

2. Using the quantitative relationship between F x vs. tan (θ) what is the mass?3. Use an electronic scale to determine the mass of the object. Does your result match the scales

readings within 5%. Why or why not?

θ

Protractor