EXPERIMENT 10: AIR TRACKS & INVESTIGATING NEWTON’S SECOND LAW
CRITERIA: 1, 2, 3, 5
AIM
To verify Newton’s Second Law
THEORY
Newton's second law of motion looks at the behavior of objects for which all existing forces are not balanced.
The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the massof the object.
The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
As the force acting upon an object is increased, the acceleration of the object is increased.
As the mass of an object is increased, the acceleration of the object is decreased.
Newton's second law of motion can be formally stated as follows:
The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
This verbal statement can be expressed in equation form as follows:
a = Fnet / m
The above equation is often rearranged to a more familiar form as shown below. The net force is equated to the product of the mass times the acceleration.
Fnet = m * a
Accessed 9th September, 2013
PROCEDURE
Set up the air track so that it is horizontal and elevated above the bench top. The end of the track should overhang the end of the bench. The clock should be set up to time over a fixed distance (one clock, two photo-gates). Take care with the setting up. Take your time.
Accessed December 6th, 2015
Part 1 a α. F (mass constant)
Add 100g mass to the glider and then measure its total mass. Attach a length of cotton to the glider with a 10g mass tied to the other end. Allow the glider to accelerate over the measured distance between the photo-gates and record the time. Repeat at least three times. Change the accelerating mass to 10g and repeat. Do this for three more masses up to 30g.
Part 2 a α 1/m (force constant)
Attach 15g to the cotton as the accelerating mass. Weigh the glider (with the card etc attached) Accelerate the glider over the measured distance and record the time. Repeat at least three times.
Add 50g to the glider and repeat. Do this for three more additions of 50g.
RESULTS
Part 1 (Changing accelerating force)
Mass of glider + card etc. = kg
Suspended mass (g) / t1 / t2 / t3 / t4 / Average time (t)10
15
20
25
30
Suspended mass (g) / Accelerating force (N) / Displacement of glider (m) / Average time (t) / Acceleration
(a= 2s/t2) (ms-2)
))
0 / 0 / 0 / 0 / 0
10 / 0.10
15 / 0.15
20 / 0.20
25 / 0.25
30 / 0.30
Part 2 (Changing the mass of the glider)
Suspended mass =g. Accelerating force =N
Accelerated glider / t1 / t2 / t3 / t4 / Average time (t)Empty glider
Glider +50g
Glider +100g
Glider+150g
Glider +200g
What is being accelerated / Mass (kg) / 1/m (kg-1) / Displacement of glider (s) m / Average time (t) sec / Acceleration(a = 2s/t2) ms-2)
Empty glider
Glider +50g
Glider +100g
Glider+150g
Glider +200g
Graph work
Draw three graphs using Excel. a vs F from the first table and a vs m and a vs 1/m from the second table. (a on the y axis for all three) or using graph paper as advised by your teacher.
Attach your graphs to this experiment.
DISCUSSION
This should include
- A discussion about the shape of the graphs and what they indicate with regard to Newton’s Second Law.
-An equation for each of the two straight lines.
-A discussion about the significance of the gradient when assessing the success of the experiment. (Would include a percentage error.)
-A discussion of any errors which might have affected the results.
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CONCLUSION
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NOTE: How to create a chart using Excel
- Select the datafor whichyou wantto create achart.
- Click InsertScatter
Scatter This chartshowsdatapoints without connectinglines tocompare pairs ofvalues.
3. Onyourchart, click the dataseries to whichyou wantto addatrendline.
4. Clickthe Chart Elements buttonnext to theupper-rightcornerof thechart.
5. ChecktheTrendlinebox.
6. Now FormatTrendlinepane underTrendlineOptions. Select the Set Intercept, Display Equation on chart and Display R-squared value on chart.
7.To add a Chart Title
8. Clickthe Chart Elements buttonnext to theupper-rightcornerof thechart.
9. ChecktheChart Titlebox. A chart title is added to the chart
10. To add Axis Titles
11. Clickthe Chart Elements buttonnext to theupper-rightcornerof thechart.
12. ChecktheAxis Titlesbox. Primary horizontal and vertical axis titles are added to the chart.
Ref: G Horner, WWalker, B Payne, K. Drysdale