# Newton's Second Law of Motion

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• Published : January 23, 2013

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E104: NEWTON’S SECOND LAW OF MOTION

METHODOLOGY
In Part A of the experiment (Constant Mass, Changing Net Force), place the dynamics track on the laboratory table. Make sure that it is horizontal by placing the dynamics cart on the track. If the dynamics cart does not move, then the track is already horizontal. Otherwise, make the necessary adjustments. Get the mass of the dynamics cart. Write this under m1 in Table 1. Set the first photogate at the 20-cm mark of the dynamics track and the second photogate at the 70-cm track. This is the distance in which the cart can travel. Write this under S in Table 1. Plug the first photogate to the number 1 slot of the smart timer and the second photogate to the number 2 slot. Ask for help from your instructor if you have difficulty in setting up the photogates and the smart timer. Set the smart timer by pressing the “Select Measurement” button until it shows “Time:”. Set the mode by pressing the “Select Mode” button until it shows “Time: Two Gates”. Tie one end of the string to the cart and the other end to the weight hanger. Set the dynamics cart on one end of the track and the weight hanger over the pulley. Refer to setup. (See Figures 2 and 3). For the first trial, use a total mass of 20g for the hanging weight. Write this under m2 in Table 1. Release the cart. Read the time of travel from the smart timer. Write the time of travel under t in Table 1. Repeat procedures 1-8 using masses of 40g, 60g, 80g, and 100g. Write the data in appropriate spaces in Table 1. Compute the accepted value of the acceleration using Equation 5. Compute the experimental value of the acceleration using Equiation 6. Compute the percentage error for each trial. From your data draw the acceleration (experimental value) vs. Net force graph.

In Part B of the experiment (Changing Mass, Constant Net Force), repeat Part A using a mass of 100g for the hanging weight. Write this under m2 in Table 2. For the first trial, get the mass of the cart and write this under total mass of cart m1. Release the cart. Read the time of travel from the smart timer. Write the time of travel under t in Table 1. For trials 2-5, add masses of 100g, 200g, 300g, and 400g to the cart and write this under total mass of cart m1. Compute the accepted value of the acceleration using Equation 5. Compute the experimental value of the acceleration using Equation 6. Compute the percentage error for each trial. From your data draw the acceleration (experimental value) vs. mass graph.

In Part C of the experiment (Changing Mass, Changing Net Force, repeat Part A changing the mass of the cart and the hanging weight for each trial. Use the following masses:

Trial| m1| m2|
1| mass of cart| 20g|
2| mass of cart + 100g| 40g|
3| mass of cart + 200g| 60g|
4| mass of cart + 300g| 80g|
5| mass of cart + 400g| 100g|

The dynamics track serves as the path for the motion of the dynamics cart. The dynamis cart is the object being observed as it accelerates on the dynamic track. The string is used to tie the end of the dynamics cart and the weight hanger. The photogates are used for detecting the motion in which the cart passed from photogate 1 to photogate 2. The smart timer is used to record the time of travel of the cart from photogate 1 to photogate 2. The set of weights are for changing the mass of the track and the net force. The weight hanger holds the weights. The pulley is a tool for pulling the cart as the weight hanger falls.

DATA AND RESULTS
Table 1. Constant Mass, Changing Net Force
trial| m1 (kg)| m2 (kg)| net force (N)| a (av) (ms2) | time (s)| a (ev) (ms2)| % error| 1| 0.52| 0.02| 0.20| 0.36| 1.80| 0.31| 14.43|
2| 0.62| 0.04| 0.39| 0.60| 1.42| 0.50| 16.51|
3| 0.72| 0.06| 0.59| 0.76| 1.22| 0.67| 10.75|
4| 0.82| 0.08| 0.78| 0.87| 1.09| 0.85| 3.01|
5| 0.92| 0.1| 0.98| 0.96| 1.01| 0.98| 1.74|
mass of cart, m1 = 0.51814 kg
distance...