E1 Mechanics and Forces - Laboratory Report
Experiment report
Student name
Student no
Grade
Preliminary Exercise
Complete the following questions on this sheet, either typed or handwritten.
In these exercises use g = 9.8 m/s2
1: In the theory document, you will find the experimental set-up for the statics lab (three suspended masses connected by a string). Ignoring friction and taking the special case where m1 = m2 = 0.1 kg and m3 = 0.15 kg.
Find 1 and 2 at the equili
ium position.
2: In Part B: Attwood’s Machine, ignoring friction and the rotational inertia of the pulley (ie. Assume the pulley is mass-less) calculate the acceleration of m2 (downwards is positive) for the case where m2 = 120 g and m1 = 100 g.
3: In an experiment using m2 = 120 g and m1 = 100 g, the measured acceleration was 0.85 m/s2. In this case assume that there is friction at the pulley but that the mass of the pulley is negligible. Determine the additional mass in grams that must be added to m2 in order to overcome this friction.
Online Experiment - Part 1 (see Static Video for demonstration)
1. The pulley system shown in Figure 1 is set up in the “Part 1 - static experiment” video with m1 = 200 g, m2 = 250 g and m3 = 300 g. A sheet of paper was placed behind the strings so that the string positions could be marked on it. This is shown below with the angles of the strings (relative to vertical) and masses (in grams) included.
2. Draw the free body diagram (as in Figure 2 of the Theory section) for this apparatus with forces, coordinate system and x/y force components clearly marked. Calculate horizontal and vertical components of forces based on equili
ium and insert these into the table at the bottom of this page. Note that due to friction the horizontal and vertical components will generally not add to zero. Use your results and equations (3) and (4) to estimate the two (x and y) components of the net frictional force.
FREE BODY DIAGRAM HERE:
Results for Part A: Addition of Forces
(Record your results for the force components below)
1
54
deg
2
43
deg
F1 = m1g
N
F2 = m2g
N
F3 = m3g
N
F1sin 1
N
F1cos 1
N
F2sin 2
N
F2cos 2
N
fnet x
N
fnet y
N
Atwood’s Machine - Part 2 (see Atwood’s Machine Video for demonstration)
Note that to save time the mass of the washers used in the experiment is given:
mwasher = 1.155 g
Enter all results in the resource spreadsheet available for download on Canvas and paste the tables/graphs into report where indicated. Use “Paste as Picture”. This will enable easy re-sizing of results to fit into your document.
1. In this experiment washers are used for small increments in mass. The total mass of the system is maintained but the difference between the two masses is altered by transfe
ing washers from one mass to the other.
2. The “Part 2 - Atwoods machine” video shows the single pulley Atwood’s machine (Figure 5 in Theory section). The experiment is performed with two different (larger and smaller) values of m1-m2.
3. For the experimental data, the washers were moved one at a time from m1 to m2 until m2 just began to move downwards (accelerate) when released. Sufficient force was then provided to overcome friction. This is your first experimental point.
4. The time required for m2 to fall a known distance (1.0 m), to the floor was measured using a stop-watch.
Five measurements were taken for each data point and averaged for the times in the Atwood’s Machine Table. You need to calculate the acceleration of the masses from these times (using the equation(s) of motion discussed in the lectures).
Paste the table with the acceleration column filled in here:
5. Now use Microsoft Excel (or similar) to tabulate results and to plot a graph of acceleration vs. (m2 - m1).
Use XY (Scatter) chart from the Chart Wizard - show points (markers) only and add a linear trend-line and check the box to Display equation on chart. As well as plotting the line of best fit (linear regression) your plot will give you the gradient and the intercept on the vertical axis.
As shown in the Theory section, the gradient of this plot enables g to be calculated and the intercept on the vertical axis enables an average kinetic frictional force to be extracted from the measurements.
Paste your graph of acceleration vs. m2 - m1 here.
Determine the gradient and intercept from the graph and use Equation (6) to calculate the acceleration due to gravity (g) and the kinetic frictional force. Comment (in your own words) on sources of e
or that may lead to e
or in your value of g.
g
m/s2
Kinetic Friction
N