Investigating an Object’s Motion: Newton's First Law and Second Law
If you push a chair across a floor, you are exerting a force on the chair. If you then drag the chair across the floor by pulling on it, you are also exerting a force on the chair. You can think of forces as a push or a pull acting on an object. Kicking a soccer ball, pulling a wagon, throwing or catching a baseball, jumping off the ground, these are examples of contact forces. When a force is exerted on an object, that object will either move or not move. What decides whether that object will move and how quickly will it move? That question can be answered by investigating Newton’s First Law of Motion and Newton’s Second Laws of Motion.
Newton’s First Law of Motion: An object at rest will remain at rest unless acted upon by an UNBALANCED NET force.
Newton’s Second Law of Motion: The change in an object’s motion is proportional to the force acting on it.
The motion of the object is determined by all the forces acting on it. Think about a game of tug of war. If nobody from either side pulls on the rope, will the rope move? If both teams pull the exact same amount, so the forces are BALANCED, will the rope move? If the team on the right side of the rope pull with more force than the team on the left side, so the forces are UNBALANCED, which way will the rope move? What do you think determines how fast the rope will move to the right or the left?
In this lesson, students plan and carry out an investigation into Newton's First Law of Motion and Newton's Second Law of Motion. This activity aligns to NGSS standard MS-PS2-2: Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object. Click here for more details on the NGSS alignment for this activity.
Students will be able to:
-Design and carry out an investigation into Newton’s First Law of Motion and Newton’s Second Law of Motion.
-Answer the Investigation Question by determining how changes in pulling forces (hanging weights) affect the motion of a cart (does the cart move? does it speed up, slow down, stay the same?)
How do changes in pulling force affect the motion of an object?
What do you predict the answer to the Investigation Question will be? Explain using your own prior knowledge or information from the Background Information section.
Procedure: Plan and Carry Out an Investigation
Your investigation will measure the motion of a cart as it is pulled across a table by the hanging weights.
Your procedure will need a step-by-step guide of how your group will answer the Investigation Question.
In your procedure, be sure to answer the following questions:
- What type of PocketLab data do you need to collect (Acceleration, Position vs Time, Velocity vs Time, etc.)?
- What is the independent variable, what is the dependent variable, and what are the control variables in the investigation?
- How will the independent variable be changed and how the dependent variable will be measured?
- How will the Data Analysis tools in the PocketLab App help in analyzing the results of each trial?
- How many Runs and Trials are needed to answer the Investigation Question?
- How will you visualize your data for analysis (table, graph, etc.)?
Data Analysis Tools
To use the Data Analysis tools in the PocketLab Web App, on a recorded data trial, highlight the portion of the graph that you are interested in by clicking and dragging with your mouse. Next, click the Data Analysis button. You should see basic statistics on the portion of the graph you’re viewing as well as the ability to add curve fits.
Follow your procedure for analyzing the results of each Trial and Run then answer the following questions:
- What did the collected data tell you about the Investigation Question?
- How did use the Data Analysis Tools and your data visualization help you determine the answer to the above question?
Was your hypothesis valid or invalid? How do changes in pulling force affect the motion of an object? How does this relate to Newton's First Law and Second Law of Motion?
How does your analysis of the collected data support your claim?
Justification of Evidence
What scientific concepts or principles can explain the evidence?