Lab 4: Newton’s 2nd Law
g by Atwood’s Machine
Ben Wildeboer
Calc-based Physics I
Three Rivers CC
September 26, 2011
Description
The purpose of this lab was to determine the value of g using Atwood’s
Machine and measuring the acceleration.
Data and Measurements
See attached sheet.
Calculations
Part I: Determining acceleration of the system
∆y = 0.650 m
m1 = .200 kg
m2 = .210 kg
average t = 2.402 s
y = y0 + 21 at2
2(∆y)
a=
t2
(2(0.650 m)
a=
= 0.2253 m/s2
(2.402 s)2
Part II: Using acceleration of the system to find g
F1 + F2 = Fg1 − Fg2
m2 a + m1 a = m1 g − m2 g
(m2 + m1 )a = (m
1 − m2 )g
m2 + m1
a
g=
m2 − m1
0.210 kg + 0.200 kg
0.410 kg
2
g=
0.2253 m/s =
0.2253 m/s2 = 9.2373 m/s2
0.210 kg − 0.200 kg
0.010 kg
9.80 m/s2 − 9.2373 m/s2
% error =
= 0.0574 or 5.74%
9.80 m/s2
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Conclusions
This lab demonstrated Newton’s 2nd law by showing unbalanced forces result
in an acceleration. Using that acceleration, we found we were able to fairly
closely approximate the value for g. Though our calculated magnitude for
g showed an error of 5.73%, this is a fairly close value considering possible
errors such as human timing, friction from the pulley, and the use of a nonmassless string.
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