Newton's Second Law
Lesson 7 of 12
Objective: Students will demonstrate an understanding of Newton's second law by completing a set of interactive activities.
The goal of this lesson is to help students construct explanations about the acceleration of an object with a mass that resists acceleration and the forces acting on an object. This lesson addresses the HS-PS2-1 standard because it asks students to use their understanding of the forces acting on an object to change the motion of that object. It aligns with the NGSS Practices of Analyzing and Interpreting Data (SP4), Using Mathematical Reasoning (SP5) and Constructing Explanations (SP6) for Science because students use their prior knowledge of forces to answer the embedded questions in an EDpuzzle on Newton's second law. Students then use an interactive website to apply a force to an object. During the closure activity at the end of this lesson, I ask students to discuss the most important and challenging parts of today's lesson on forces and Newton's second law.
I assess student understanding throughout the lesson using informal check-ins and assess each student's work at the end of the school day. I want students to learn to integrate information from various points of this course into a conceptual understanding of Newton's second law. One goal of this lesson is to help students learn that objects accelerate in the direction of a net force.
This portion of the lesson begins with a routine where students write the objective and additional piece of information in their notebooks as soon as they enter the classroom. I project a slide with the date, the objective and an additional prompt on the interactive whiteboard with a red label that says "COPY THIS" in the top left-hand corner. Sometimes the additional prompt is a BIG IDEA for the lesson or the Quote of the Day or a Quick Fact from current events that is related to the lesson. The red label helps my students easily interact with the information as soon as they enter the room and avoids losing transition time as students enter the classroom.
Today's additional piece of information is a Big Idea which states that objects in equilibrium do not accelerate. The objective of the bell-ringer is to give students a clear understanding of the focus of today's lesson. I want students to learn that objects accelerate in the presence of a non-zero net force.
Within this lesson, I introduce a mathematical model for the Newton's second law. I include a set of notes that I project at the interactive whiteboard in the front of the room. This part of the lesson focuses on the mathematical model for Newton's second law. For the first ten minutes, I play the notes at the front of the room for the entire class and pause at the pause points I embed as green question marks in the video.
During the first ten minutes, students take notes in their notebooks. I ask students if they have any questions or concerns about the methods discussed in the video. We have a whole class discussion for 2-4 minutes. Some student queries include, "Is there a way to apply a force and not cause a change in motion?", and "What happens if I throw the ball on a windy day?" During the last minute of this section of the lesson, I email this video and notes to the entire class so that students can watch, pause and replay the video outside of class. During the next section, students are given a set of activities related to these notes to complete in pairs.
During this section, I spend 1-2 minutes distributing Chromebooks and two sets of handouts to students. Each student team consists of four students. Each student in the team must use the interactive to investigate the variables that affect an object's acceleration and the net force required to accelerate an object. This activity asks students to spend twenty minutes testing the effect of holding either mass or applied force constant on the resulting acceleration of an object. The first activity is in a frictionless environment while the second activity takes friction into account.
While student teams spend twenty minutes discussing the data they gather using the interactive activity with their table mates, I circulate and address any questions students may have. During the twenty-minute period students spend working with the interactive activity, students first click the activity link I post on our Edmodo wall, then test ten trial outcomes using different combinations of applied force and mass. Students record the data in a table and analyze the effect of changing mass or net force on the acceleration of the object. To determine the acceleration of the box, students have to determine the slope of a velocity vs time graph which I introduce in an earlier lesson. Student teams create a claim using the data from the interactive activity.
Once student teams collect the data and create a claim, students discuss the strengths of the evidence each member uses to support the claim in a 10-minute roundtable discussion. Some student responses include, "Doubling the mass decreases the acceleration of the box.", "Objects that move have an unequal set of forces," and "I like that the interactive tells me when I choose the correct forces but have incorrect sizes or directions instead of just saying that my diagram is incorrect". After ten minutes pass, I ask students to spend the next five minutes completing the conclusion section of the activity using information from their roundtable discussions.
At the end of this section, I collect the activity to grade and return to students later in the week. Click here, here, and here to see examples of student work. I choose these activities because I want students to understand that objects accelerate when forces are unbalanced or an object experiences a non-zero net force.
This closing activity asks students to write a short summary of the most important part of today's lesson in their notebooks. Some student responses include, "Using the interactive to find the acceleration of the box." and "Comparing the acceleration of an object both with and without friction for the same applied force". I like this activity because it gives students a chance to voice their current level of understanding and their thinking about their learning processes based on today's lesson.
To wrap up, I ask students to read section 4-4 on Newton's second law of motion in the openStax textbook for homework. I ask that they write the solutions to the exercises at the end of the section in their notebooks.