Sample lab report for introductory physics
This sample lab report for introductory physics can be used for an introductory physics lab course in a community college or university. The format could also be used for an intermediate/advanced lab in any physical science course.
Experiment 1: Determination of Coefficient of Restitution of Concrete Floor
Author: Benjamin O. Tayo
Lab Partners: Eric Mullins and Michael Anderson
Abstract
The coefficient of restitution (e) is an important quantity that characterizes the nature of different surfaces. It is a quantitative measure of the fraction of kinetic energy transferred to a surface when an object strikes the surface. e generally takes values in the range [0,1]. Our experiment revealed an e value of 0.75 for a concrete floor impacted upon by a tennis ball. The calculated value of e was then used to predict a 44% energy transfer from the ball to the floor.
Keywords: Coefficient of restitution, kinetic energy, potential energy, conservation of energy
Objectives
The initial height x0 of a tennis ball above the floor is measured. The ball is released so that it strikes the concrete floor and rises to some final height x1. The change in height is then calculated as dx = x0 - x1. We expect a linear relationship between dx and x0, that is:
This relationship will be tested, and if it holds, will be used to determine the coefficient of restitution e. Once the e value is known, we will use it to calculate the fraction of kinetic energy transferred from falling ball to the concrete floor.
Procedure
The following apparatus was used: a meter stick and triple beam balance. The mass of the ball was recorded using a triple beam balance. The ball was dropped from some initial height x0 which was measured using a meter stick. After bouncing off the floor, the final maximum height was recorded as x1. The change in height due to kinetic energy loss was calculated by subtracting the final height (x1) from the inital height (x0), that is, dx = x0 - x1. Several trials were performed, for each trial corresponding values of x0 and x1 were recorded, and dx was calculated accordingly.
Data and Analysis
A total of 10 trials was performed. The data collected is tabulated in Table 1. Figure 1 shows a graph of dx plotted as a function of x0.
From Figure 1, we see that the best fit line fits the data pretty well, except for some slight deviations due to uncertainties. This result confirms the linear relationship between dx and x0 as predicted by Eq. (1). The slope (s) of the best fit line is s = 0.44. Using Eq. (1), we can show that the e value can be obtained from the slope using:
By applying the principle of conservation of energy, the fraction of kinetic energy transferred to the ball after it strikes the floor is given by
Using the value for e, we calculated the transferred kinetic energy as E1 = 0.56 E0. This means that only 56% of the initial energy of the ball is retained after the impact. About 44% of the ball’s energy is absorbed by the concrete floor.
Conclusion
The experiment validates the theoretical prediction that dx increases linearly with x0. The data collected supports this notion very well as most of the data points fit nicely with the linear fit. The fitted line shows small deviations, which might be due to uncertainties associated with the measurement of the final height of the ball. The data was then used to obtain an e value of 0.75 for the concrete floor. Using our e value, we also predicted that 44% of the initial kinetic energy of the ball is absorbed by the concrete floor after the impact. Overall, the experiment was successful and the calculated values were meaningful. The experiment has helped me to gain useful insights on how energy is transferred in a non-conservative collision process.
