Newton's Second Law of Motion

Introduction

Newton's second law of motion, F = ma, describes the relationship between force, mass, and acceleration. The equation tells you that acceleration is directly proportional to the net force acting on an object, and it is inversely proportional to the mass of the object.

Objective

To understand the relationship between force and acceleration in a system near the surface of the earth.

Equipment

• TI 82
• CBL interface
• dynamics cart
• smart pulley
• string
• masses

Procedure

1. Attach a string to a cart and pass the string over a smart pulley, which is clamped to the edge of a lab table.
2. Attach the TI-82 and CBL to the smart pulley.
3. Load masses on your cart and on the string hanging from the smart pulley so that
4. the total load is always 200 grams.
5. Turn on the calculator and the CBL and use the program, "Photogate Timing with the CBL."
6. Allow the mass on the string to fall and pull the cart across the table while the calculator accumulates the times and position readings.
7. Perform at least five trials, each with a different mass on the hanging string.

Observations

Compare each graph you see on your calculator with the graph on the next page, which is a composite graph, i.e., position vs. time, velocity vs. time, and acceleration vs. time. The graph on the next page was made using the same procedure you used with an unknown net force.

Use the analyzing feature of the calculator to read y-values off the three types of graphs on your calculator.

Conclusion

Write a brief but complete statement describing the relationship between force, mass, and acceleration.

Written by Frank Mudrak, July 1997