Download Force (Weight versus Mass): Newtons 2nd Law

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Status: Published
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Resource ID#: 51128
Force (Weight versus Mass): Newton's 2nd Law
Students will examine the relationships between mass, force and acceleration, applying Newton's 2nd Law.
This is part 2 of a two-part lab. It is recommended that the teacher cover the first lesson (Linear Motion, ID 51003) prior to completing this lesson.
Subject(s): English Language Arts, Science
Grade Level(s): 8
Intended Audience: Educators
Suggested Technology: Overhead Projector,
Microsoft Office
Instructional Time: 1 Hour(s)
Resource supports reading in content area: Yes
Freely Available: Yes
Keywords: force, mass, Newton, law, acceleration, scale, distance, displacement
Instructional Design Framework(s): Confirmation Inquiry (Level 1), Guided Inquiry (Level 3), Cooperative
Learning
Resource Collection: CPALMS Lesson Plan Development Initiative
ATTACHMENTS
Forces Lab Report Rubric.xlsx
Force Lab Activity.doc
Force Unit Guide.docx
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will:
learn to differentiate between mass and weight.
be introduced to Newton's Second Law of Motion (F=ma).
learn about instrument calibration (using a spring scale).
examine possible causes of error (review accuracy and precision).
be introduced to the SI units of measurement for Force and mass.
Prior Knowledge: What prior knowledge should students have for this lesson?
Students should know how to plot a graph with data and calculate slope.
Guiding Questions: What are the guiding questions for this lesson?
What is the difference between weight and mass?
How does Newton's 2nd Law of Motion relate weight and mass?
Teaching Phase: How will the teacher present the concept or skill to students?
As a whole group activity:
Ask students questions about forces in real life situations:
page 1 of 3 What is the difference between mass and weight?
When do we use mass and when do we use weight?
Is there a difference between force and weight?
What is the formula for calculating force? F = ma
How can we manipulate this formula?
What are the units used in each part of the formula?
As students answer, address common student misconceptions about force:
Rest is the "natural" state of motion in which no forces are acting on an object. If there is no motion, then there are no forces acting.
Passive objects (stationary rope, table top) cannot exert a contact force.
An impelling force (impulse or impetus) can become part of an object.
A constant force produces a constant speed. Under the influence of a constant force, objects move with constant velocity.
Increasing speed requires increasing force.
When a force acts on an object in the direction of the object's motion, the speed of the object will increase for a while and then level off at the higher speed.
If an object is slowing down, a force that was moving it forward must be decreasing.
When a force acts on a moving object in the direction opposite the object's direction of motion, the object will move at a constant speed for a while and then slow
down.
Moving objects stop when they run out of force.
A moving object has a force within it that keeps it moving.
A constant force is needed to keep an object moving at constant speed.
A force is required to keep an object moving. Objects slow down and stop if a force is not maintained.
When an object is moving at a constant speed, there is a force in the direction of motion (inertia is a force).
Friction, not inertia, is the principle reason objects remain at a rest or require a force to move.
The SI measurement for Force is the Newton, the SI measurement for mass is the gram (in this case we are using the kilogram). The SI unit for acceleration is
m/s2.
As you go through the explanations students can record this information in their notes, this will be needed later as they write up their lab report.
Lab Activity - Hand out the Force Lab found attached. Have students complete the lab working in groups.
Follow up - Have students complete a full lab report that will be graded using the attached rubric.
Guided Practice: What activities or exercises will the students complete with teacher guidance?
As the teacher discusses important points (the questions in the Teaching Phase), the students will model the concepts on their mini white boards. They can also record
this information in their notebooks.
Go through demonstration of calibration of a spring scale. Review the importance of calibration in science. What does this mean? How do we calibrate the spring
scale? What units are we using? (grams or kg and Newtons)
Review how to use the spring scale, and remind them how to refrain from stretching out the spring.
Demonstrate the lab activity to verify Newton's 2nd law and determine the link between force and weight.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
Practice: Students will conduct investigations in lab groups on the relationship between force and weight. See lab activity attachment.
As students conduct lab in groups, students will complete lab sheet. The teacher will circulate to make sure students are on task and following procedures.
After students finish the lab, next, they will write up a lab report summarizing their findings. Use the lab report rubric to review with students the expectations for their
report.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
The teacher will review the lab results with students upon completion of the lab and submission of lab reports.
Summative Assessment
Students submit a lab report on their findings and make suggestions on how to improve the lab. To evaluate the lab report, use the following rubric: Forces Lab rubric
Formative Assessment
Newton's Second Law basically states that unbalanced forces cause acceleration. To explore this law, use a spring scale that gives a reading of the force (F) in Newtons
(N) exerted by the spring. If we hang a weight from this scale it will give a reading that we will call F1.
Class Activity: Have each group come up with a procedure to perform this lab and present it on a whiteboard. In this activity, the groups also included comments as
well as Higher Order Thinking (H.O.T) questions.
Sample H.O.T Questions:
Where have you seen the value of your slope before?
What would change on the moon or other planets and what will stay the same?
What happens to your graph if you use mislabeled masses?
If you are in an elevator, explain how the reading can change?
Predict the reading of the force with a mass of 1kg when the scales are one after the other and one next to each other.
Feedback to Students
Students will divide into groups and work on the included lab activity (see attachments). The teacher will circulate among the groups to check for understanding and
correct practices.
ACCOMMODATIONS & RECOMMENDATIONS
page 2 of 3 Accommodations: Identify students' abilities (gifted students, special needs students) and group students with mixed ability levels.
Extensions: Select problems using the formula F=ma from your textbook to practice as homework/class work.
Use online resources to practice problems such as:
http://www.physicsclassroom.com/class/newtlaws/u2l3a.cfm
http://www.mazzworld.net/U3Q1.html
Suggested Technology: Overhead Projector, Microsoft Office
Special Materials Needed:
One per group:
Balance
Slotted mass set
Mass hanger
Spring scale
Clamp
Ring stand
Meter stick
Small white boards (2' x 2')
Dry erase markers
Per student:
Lab Activity sheet
Further Recommendations: Test out the measurements and lab before using it with your students to make sure the spring scales and such work properly.
Additional Information/Instructions
By Author/Submitter
This lesson specifically addresses Newton's 2nd Law, so it doesn't fully cover the Standard SC.8.P.2.
Newton's First Law is covered in a previous lesson, Linear Motion.
SOURCE AND ACCESS INFORMATION
Contributed by: Taiwo AdeifeOsemeikhian
Name of Author/Source: Taiwo AdeifeOsemeikhian
District/Organization of Contributor(s): Miami-Dade
Is this Resource freely Available? Yes
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
SC.8.N.1.1:
SC.8.P.8.2:
LAFS.68.RST.1.3:
Description
Define a problem from the eighth grade curriculum using appropriate reference materials to support scientific
understanding, plan and carry out scientific investigations of various types, such as systematic observations or
experiments, identify variables, collect and organize data, interpret data in charts, tables, and graphics, analyze
information, make predictions, and defend conclusions.
Differentiate between weight and mass recognizing that weight is the amount of gravitational pull on an object and is
distinct from, though proportional to, mass.
Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical
tasks.
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