LAB #5: Dynamics
Theory:
Define Newton’s Second Law. What is Atwood’s machine? Draw it and explain how it
works (what forces are present and how they act upon 2 masses)? Why the system
accelerates? Draw free body diagram and write equations of motion. Also write down
equations for acceleration and tension in Atwood’s machine.
Experiment:
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Consider Mtot=m1+m2 and Fnet=( m2- m1)⋅g= Mtot⋅a
Begin with m2≈320gr and m1≈250gr (including 50gr mass holder). Record actual
masses.
Mtot=(____±_____)gr.
With m2 initially in the floor, release it.
The computer will plot v vs. t as m2 falls; the slope is ameas.
Repeat 4 times keeping Mtot constant (≈570gr) and transferring 10 gr from m2 to
m1.
m1±δm1 (gr)
m2±δm2 (gr)
≈250
≈260
≈270
≈280
≈320
≈310
≈300
≈290
ameas ±δameas(m/s2)
Data analysis:
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Calculate Fnet=(m2-m1)g for each run. Do not calculate δFnet
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Plot Fnet vs. ameas in JagFit ; slope is b ± δb
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Calculate the total mass of the system Mtot=m1+m2 and δMtot for first run only.
If the N2L is valid the slope b should be equal to Mtot
Compare the JagFit slope b ± δb with actual mass of the system (Mtot) to prove
Newton 2nd Law.