Cruising with Sir Isaac

Background Information

Sir Isaac Newton published his three laws of motion in a book titled The Principia. This work is widely regarded as one of the most important scientific achievements of all time. Newton’s Laws established the fundamental principles that govern the motion of objects. Newton’s investigations stimulated a flourishing of mathematical and scientific thought that led to the development of the fields of calculus, statics, dynamics, celestial mechanics, and essentially gave rise to most areas of modern engineering. In this lab, you will examine the motion of a moving object in order to develop a conceptual and mathematical understanding of Newton’s Second Law of Motion.

Procedure – Part 1

1. Obtain the necessary lab materials and set up the apparatus as demonstrated by the instructor. Note all

materials used and list them in your lab report. Use care when adjusting the photogate position

2. Draw a quick sketch of the apparatus that you can reproduce in your lab report.

3. Mark start and end points, and measure the displacement to the photogate timer. Record on data sheet.

4. Add 3 kg of mass to the dynamics cart. The mass will be kept constant for this part of the experiment.

5. Apply a force of 0.5 N to the end of the string and record the time that is takes for the cart to accelerate

from the starting point to the photogate timer. Be careful to stop the car before it crashes

6. Repeat step #5 for forces of 1.0, 1.5, 2.0, and 2.5 N

7. Calculate the acceleration of the cart. Record the equation that you used on your data sheet.

8. Plot a graph of Acceleration vs. Force and analyze the graph using standard techniques.

Procedure – Part II

1. Obtain the necessary lab materials and set up the apparatus as demonstrated by the instructor. Note all

materials used and list them in your lab report. Use care when adjusting the photogate position

2. Mark starting and end points, and record the displacement to the photogate timer.

3. Find and record the mass of the empty cart using an electronic balance.

4. Apply a force of 0.5 N to the end of the string. Record the applied force on data sheet.

5. Record the time that it takes for the cart to travel from the starting point to the photogate timer, and

calculate the acceleration of the cart.

6. Add an additional 1 kg of mass to the cart and record the total mass of the cart plus 1 kg in the first

column of your data table. Repeat step 5, and continue until you have added a total of 5 kg of

additional mass to the cart.

7. Plot a graph of acceleration Vs mass and analyze the graph using standard techniques.

(Hint: think about the special cases of zero mass and infinitely large mass)

Analysis of Results:

Plot graphs for both parts of the experiment. Use standard techniques to obtain straight-line graphs and determine the slope and intercept for each of the lines. For each graph determine the physical significance of the slope and intercept and write a mathematical equation for the line. Include this information in the graphical analysis section of your lab report.

Determine the percent error for both parts of the experiment. Record the observed and accepted values with your error calculations on your data sheet. Discuss this information and identify sources of error in the error analysis section of your lab report. Provide suggestions on how errors might be eliminated or minimized in this experiment.

Lab Report – In addition to the standard lab report items, please include the following:

1. Formulate a hypothesis for your experiment relating acceleration, force and mass.

2. List materials and explain the procedure used in the methods section of your lab report.

3. Include a diagram or sketch illustrating the set up of the apparatus used in the experiment.

Questions:

1. What was the independent variable in Part I? What was the dependent variable?

2. If the force on an object is increased, what happens to the acceleration?

3. What was the independent variable in Part II? What was the dependent variable?

4. If the mass of an object is increased, what happens to the acceleration?

5. Objects with more mass have (more/less) inertia?

6. The inertia of object a is twice that of object b. What can you say about the forces required to

accelerate the objects at a rate of 7.0 m/s/s?

7. A force is applied to an object and its acceleration is observed. In a second trial, the mass of

the object is quadrupled and the same force is applied. How do the two accelerations compare?

8. State Newton’s 1^st law in words.

9. State Newton’s 2^nd law in words.

10. State Newton’s 2^nd law as a mathematical equation.

Newton’s 2^nd Law Experiment NAME _____________________________

Data Tables HOUR _____________

DATE _____________

Part I

Displacement (Dd ) = ______________________

Equation used to calculate acceleration:

Experimental Error For Part I Equation used to find % Error:

Observed value = _______________

Accepted value = _______________

Percent Error = _______________