Purpose:

To explore the relationship between force, mass, and acceleration as predicted by Newton's Second Law of Motion.

Introduction:

Newton's 2nd Law states that an unbalanced force applied to a mass produces an acceleration according to F=ma. When no such force acts on a body, such as a cart, the cart either remains at rest or continues to move in a straight line at constant speed.
Because of friction, the 2nd Law seems to contradict common experience. In driving a car for example, a constant force is required to keep the car moving with constant velocity. If the force is removed, the force of friction brings the car to a stop. In the absence of friction however, the car would continue to move with constant velocity after the force is removed. The continued application of force would therefore result in acceleration.


Instructions:

  1. Each person in your lab group must read every page in this online procedure. Along the way, there will be questions that you must answer.
  2. Designate one person in your group as the Data Recorder. This person should open the Google document Experiment 6 - Force and Acceleration for the approved answer template.
  3. When this Google document opens, sign in to your Google account.
  4. From theFILE Menu, chooseMake a copy...
  5. From theFILE Menu, chooseRename...and rename the document as follows: Exp 6 - Period (1, 3, 6, or 8) - Group #.
  6. Share this document with the members of your group and with Mr. Skubis at HSTScience@gmail.com.
  7. As a group, answer all questions. Remember to use complete sentences and be mindful of grammar, spelling, and punctuation.
  8. As an individual, you will complete Calculation Requirements as specified below.
  9. Finally, AS A GROUP write a CONCLUSION as described at the end of this lab. Submit the conclusion on the Google document for full credit.
  10. REMEMBER: **Plagiarism** is a form of **Academic Dishonesty** which carries harsh consequences. DO YOUR OWN WORK!

Procedure:



force&acc.jpg



Part 1 - Constant Mass, Variable Force

  1. Secure a recording timer to the lab table with a large C-clamp. Clear a path from the timer to the edge of the table over which a dynamic cart will travel. Clamp a pulley to the table at the end of the path.
  2. Attach a length of timer tape to the back end of a dynamic cart and pass it through the recording timer.
  3. Attach a piece of string to the other end of the cart.
  4. Load the cart with two 50-gram masses, one 100-gram mass, and two 200-gram masses.
  5. Place the string over the pulley and fasten a small mass to the end to offset the frictional force on the cart. The mass is correct when the cart moves uniformly forward when given a push. This counterweight should remain on the string throughout the experiment but it is NOT recorded in the data.
  6. For the first trial, remove a 50-gram mass from the top of the cart and place it on the end of the string. Hold the cart while placing the tape in the timer.
  7. Start the timer and release the cart.
  8. Stop the cart and the timer when the 50-gram mass hits the floor. DO NOT LET THE CART HIT THE PULLEY!
  9. Remove the tape and label it TRIAL 1.
  10. Repeat this procedure for trials 2-5 using the masses indicated in Data Table 1.

Part 2 - Constant Force, Variable Mass

  1. For trials 6-10, keep 300-grams on the string (in addition to the counterweight).
  2. Following the mass guidelines in Data Table 2, repeat the experiment.


Analysis/Calculations

  1. Count the number of dots on each tape BUT do not include any dots that were recorded before the cart began to move or after the accelerating mass hit the floor.
  2. Now measure the distance between the first and last dot you counted on each tape.
  3. Record the number of dots and distance for each trial.
  4. Calculate the total time for each trial by multiplying the number of dots by the period of the timer. (Period of timer = 0.0167 sec)
  5. Calculate the force exerted by the accelerating mass.
  6. Finally, calculate the acceleration of each trial using the equation: keeper4.jpg

Graphs

  1. Using the data for trials 1-5, plot a graph using accelerations as the x-axis and accelerating forces as the y-axis.
  2. Using the data for trials 6-10, plot a graph using TOTAL MASS as the x-axis and the accelerations as the y-axis.
  3. Instructions for graphing using Microsoft Excel can be found here.