February 24, 2012
Lab #8: Newton’s Second Law and Acceleration Due to Gravity Purpose:
To observe a few effects of constant force and varying mass, constant mass and varying force and varying both mass and force and relate them to Newton’s Second Law. Apparatus:
Theory and Background:
Newton’s Second Law of Motion states that the acceleration of an object is produced by a net force that 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. Procedure:
We used Gate Timing with Acceleration software and photogate system to measure the time it takes for the glider to travel through both photogates. We had to level the air track by placing the cart at the middle of the track with the air blower on and adjusting the leveling screws on the legs of the track to get minimum movement of the cart. The cart should slowly oscillate back and forth by 10 cm to give more accurate data. The photogates were placed at least 50 cm apart and aligned so that the flag can pass through them without touching the photogates. We attached the hook and flag onto the cart and then attached the pulley to the end of the air track. A nylon line was attached to the hook of the cart and passed through the pulley with a hanger attached on the end. The hanging weight must not hit the floor before the cart flag passes completely through the second gate or it will give inaccurate data. We also weighed the cart with hook and flag attached and measured the flag length and entered the flag length into the program so it can calculate the velocities at each gate.
For the constant force part, the hanger weight remains constant and the weight of the glider will be changed for each trial; a total of five trials with different cart weight each time. For the first trial, we attached 50 grams onto the hanger weight and did not add any additional weights onto the glider, so it is just the weight of the glider itself. We added 20 grams of weight onto the glider for each trial, while keeping the hanger weight constant. We took the data for the five trials by clicking start on the program which measures the length of time for which each photogate is blocked and the time from unblcking the first gate, to blocking the second gate. It is important to always balance the same weights on both sides of the cart to eliminate friction on one side with the air track.
The next part is constant mass; we started out with 80 grams of weight attached to the glider and 50 grams of weight on the hanger. For each trial, we transferred increments of 20 grams of weight from the glider onto the hanger and we did this for five trials. This is to observe the varying force while maintaining a constant mass of the system by just changing the weights between the glider and hanger but keeping the same mass of the system.
The last part is varying force; we kept the glider weight constant while changing the weights on the hanger in increments of 20 grams for each trial. We started out with 20 grams on the cart, which will remain constant and the hanger with 50 grams. For a total of five trials, we increased the hanger weight by 20 grams each time. This is to observe the varying system-mass and the system driving force. Data:
Constant Force Data:
Glider = 199.6 grams
Hanger = 5.0 grams
Flag = 10 cm Trial
| Hanger + mass (g)
| Cart + mass(g)
| System Mass (g)
| vi (m/s)
| vf (m/s)
| ∆v (m/s)
| ∆t (s)
| a (m/s2)
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