Purpose: to examine the validity of the statement: In the absence of all other external forces except gravity, a falling body will accelerate at 9.8 m/s^2.
To be able to imitate the motion of a freely falling body, we will be using a free fall apparatus in the lab. The free fall apparatus will produce a data recorded by the spark sensitive tape in every 1/60 of a second. The data(marks) will be used to make a distance vs time graph and velocity vs time graph. By using the data and graphs, we will be able measure g, the acceleration due to gravity.
How to use the apparatus?
Pull the spark sensitive tape behind the vertical post of the apparatus and clip it with a weight to keep it in place. Turn the dial hooked up to the electromagnet up, then hang the wooden cylinder on the electromagnet. Turn the power of the sparker and the spark button on. Turn the power of the electromagnet off to drop the cylinder. After the cylinder landed, turn the power of the sparker off and tear of the spark sensitive tape for data.
*Behr Free Fall Apparatus
After producing the data on the tape, we took a meter stick and placed the 0 cm mark on one of the dots. We measured the distance/position between each dots. We then entered this data in Excel and made a table with time, distance, and ∆distance(distance - last distance). With these data, we were able to find the mid-interval time and mid-interval speed of each row. We graphed both mid-interval time vs mid-interval speed and distance vs time.
*Data(distance, time, mid-interval speed, mid-interval time) and Graphs(distance vs time, mid-interval speed vs mid-interval time)
In class we gathered the data g(slope of the mid-interval speed vs mid-interval time) to observe any deviation in our data results. Also, for us to be able to determine any uncertainty in the experiment.
We determined the have an absolute deviation of 0.203 m/s^2.
*Graph to determine the classes' uncertainty in our experiment
1. Because the graph of the of the velocity is linear, the middle time interval is the same as the average velocity.
2. We can get the acceleration due to gravity from the velocity vs time graph by determining the slope of the line. We obtained 9.50 m/s^2. A little lower to the accepted value of acceleration due to gravity, which is 9.81 m/s^2.
3. We can get the acceleration due to gravity from the position vs time graph by getting the derivative.
1. The values of g that are obtained are similar to each other, except for one value(880) that is too low.
2. The values of g obtained by the class are lower than the the accepted value of 9.81 m/s^2.
3. There is no pattern, but most of them are around 900-980 cm/s^2
4. One of the systematic errors would be the friction generated by the cylinder and the rod. As the cylinder drops, it could generate friction and slow down the drop. That could explain why most of the g values are lower than the accepted g value. One random error may be the process of obtaining the value of 880 cm/s^2.
