Labs

Students will construct series and parallel circuits with both bulbs and resistors. The lab begins with bulbs, but since taking measurements with bulbs can often be imprecise, the measurement portion of the lab uses resistors and a DC power supply.

Two marbles will roll simultaneously on different paths, starting and ending at the same height. Students will predict and then observe the results of a “race” between the two marbles, and explain the results. Quantitative analysis of the motion will be done with photogates.

Use a liquid accelerometer to observe different types of motion and classify the acceleration. Students will observe straight-line motion (constant velocity and constant acceleration), and then take their knowledge of the water’s behavior to more complex circular and pendulum motion. They will discover the centripetal (toward the center) acceleration of circular motion, and the acceleration toward equilibrium of a pendulum system.

The first experiment will use very basic equipment to measure an important quantity, the acceleration of an object in freefall. This is also known as the acceleration due to gravity, or g. The acceleration due to gravity is nearly the same at all points on the earth’s surface, 9.8 m/s2. You will compare your result to this accepted value. The second experiment will use a data-logger and photogates to measure the acceleration due to gravity. The “picket fence” has been used since photogates were developed to measure acceleration. The “pickets” block the photogate in sequence, giving a series of velocity readings. Using the velocities and the times between those velocities, the data-logger (or the student) can calculate the acceleration of the picket fence. The third experiment will use a data-logger and motion sensor (or sonic ranger) to measure the acceleration due to gravity.

Two experiments. Choose one. In the first, students are guided through the process of testing 3 variables; mass, length, and amplitude; to determine which affects the frequency of a simple pendulum. In the second, students use inquiry and experimental design to test the same variables.

Students predict and then measure, using a motion sensor, the changing position, velocity and acceleration of a simple pendulum. Graphing the motion leads to a discussion of the total force on the pendulum at different points in its motion.

A pendulum with its mass spread throughout its length is called a physical pendulum. A typical clock pendulum is an example. Students will observe a physical pendulum and measure its period, and then construct a simple pendulum with the same period. They will see that a physical pendulum acts as if its mass is concentrated at its center of mass.

Students will test two variables, to determine their effect on the pendulum’s period. Just as objects with different masses accelerate in free-fall at the same rate, changing the mass of a simple pendulum will not change its period. Changing the length of the pendulum does effect the period, with shorter pendulums having shorter periods.

The ticker tape timer works by making dots on a paper tape at equal time intervals (approximately every 0.1s in this experiment). It is an excellent way for beginning physics students to experience the measurement of motion. Students will record and graph the motion of a car that moves with constant acceleration. Results of this lab are typically very good. The velocity vs. time graph will be a straight line with positive slope, where the slope is equal to the car’s acceleration. The position vs. time graph will be a parabola.

This experiment will use photogates to find the speed and acceleration of a car rolling down a ramp. Photogates use a single beam of ultraviolet light which goes from one arm of the gate into a receiver in the other arm. A data logger connected to the photogate will record the time that the beam is blocked by an object passing through the gate. Photogates allow us to accurately measure times that would be too short to measure with a stopwatch.