Physics Lab - Newton's Second Law
The purpose of this experiment is to validate Newton's Second Law of Motion. In part A the lab cart will be accelerated by various net forces while keeping mass constant. In part B the lab cart will be accelerated by a constant net force while its mass is varied. The goal is to determine the relation between acceleration and force and the relation between acceleration and mass. The force on the lab cart is controlled and provided by gravity acting on a weight at the end of a string that passes over a pulley at the end of a lab table.
Instructions:
• Go to http://www.walter-fendt.de/ph14e/n2law.htm
• Keep the default setting for s (0.500 m) and µ (0.000)
Part A
• Set M = 99 g and m = 1 g
• Click the START button.
• Record the acceleration value.
• Click the reset button.
• Repeat the experiment and fill the table below. Force data is collected by calculating the weight of the calibrated masses added to the end of the string. (g= 9.81 m/s²)
|
M (g)
|
m (g)
|
a (m/s²)
|
F=mg (N)
|
|
99.0
|
1.0
|
.098
|
|
|
98.0
|
2.0
|
.196
|
|
|
97.0
|
3.0
|
.294
|
|
|
96.0
|
4.0
|
.392
|
|
|
95.0
|
5.0
|
.491
|
|
|
94.0
|
6.0
|
.589
|
|
|
93.0
|
7.0
|
.687
|
|
|
92.0
|
8.0
|
.785
|
|
|
91.0
|
9.0
|
.883
|
|
|
90.0
|
10.0
|
.981
|
|
In this part of the experimentmass is removed from the cart and placed on the end of a string passing over a pulley. By doing this the amount of net force will be varied while keeping constant the total amount of mass (100 g) being accelerated. It is important to note that the pull of gravity on the dangling mass causes not only the cart and its contents to accelerate, but also the string itself and the mass or masses attached to the end of the string. Put another way, the weight on the end of the string causes all of the mass to accelerate (and it all accelerates at the same rate).
Use these results to construct a force vs. acceleration graph. For this graph,plot the independent variable (force) on the y-axis.Determine the best fit.How does the shape of this graph look? What does this imply about the relationship between force and acceleration when the mass is constant?
Part B
• Set M = 100 g and m = 10 g
• Click the START button.
• Record the acceleration value.
• Click the reset button.
• Repeat the experiment and fill the table below.
|
M (g)
|
m (g)
|
a (m/s²)
|
M + m (g)
|
F=mg (N)
|
|
100.0
|
10.0
|
.892
|
|
|
|
110.0
|
10.0
|
.818
|
|
|
|
120.0
|
10.0
|
.755
|
|
|
|
130.0
|
10.0
|
.701
|
|
|
|
140.0
|
10.0
|
.654
|
|
|
|
150.0
|
10.0
|
.613
|
|
|
|
160.0
|
10.0
|
.577
|
|
|
|
170.0
|
10.0
|
.545
|
|
|
|
180.0
|
10.0
|
.516
|
|
|
|
190.0
|
10.0
|
.491
|
|
|
Use these results to construct an acceleration vs. 1/total mass graph. On this graph the x-variable is the reciprocal of the total mass being accelerated. How does the shape of this graph look? What does this imply about the relationship between acceleration and mass when the force is constant?