Calculating Net Force Activity: 8 Hands-On Stations for Teaching Balanced Forces, Unbalanced Forces, and Free-Body Diagrams (TEKS 6.7B)

Chris Kesler · 8 min read

Stand a 6th grader in the middle of a tug-of-war rope with two people pulling equally hard on each side. The rope is taut, the kids are straining, and yet nothing moves. Now ask, "Are forces being applied? If yes, why isn't anything moving?" That contradiction (forces present but no motion) is the gateway into TEKS 6.7B. Once kids understand that two equal forces in opposite directions cancel out to zero, the whole language of balanced and unbalanced forces clicks into place.

The standard asks 6th graders to calculate net force in a horizontal or vertical direction using diagrams and to determine whether forces are balanced or unbalanced. They have to draw free-body diagrams with vectors (arrows that show both size and direction), add forces in the same direction, subtract forces in opposite directions, and predict what an object will do based on the result.

The Calculating Net Force Station Lab for TEKS 6.7B closes the gap in one to two class periods. Kids run a three-part spring-scale investigation pulling a real object with measured forces (50 N vs. 75 N from opposite sides, 50 N vs. 50 N from opposite sides, two 50 N pulls from the same side). They examine reference photos of a tug-of-war, rock climbing, and a volleyball match and decide if the forces are balanced or unbalanced in each. They sort six force diagrams into matching net-force values (130 N right, 25 N left, 0 N balanced, 350 N down). By the end, they can look at any free-body diagram and tell you the net force and what the object will do next.

⏱ 1–2 class periods 📓 6th Grade Science 🧪 TEKS 6.7B 🎯 Built-in differentiation 💻 Print or Digital

8 hands-on stations for teaching how to calculate net force

A station lab is a student-led activity where small groups rotate through 8 stations (plus a 9th challenge station for early finishers) at their own pace during one to two class periods. You become a facilitator instead of a lecturer. You walk around, spot-check, and break misconceptions while kids work through the rotation.

The Calculating Net Force Station Lab has four input stations (where students take in new info on balanced forces, unbalanced forces, net force, free-body diagrams, and vectors) and four output stations (where they show what they learned). Here's what's at each one.

Inside the Calculating Net Force Station Lab printed download — 6th grade physical science, TEKS 6.7B

Sample task cards from the Calculating Net Force Station Lab — 6th grade physical science, TEKS 6.7B

4 input stations: how students learn to calculate net force

🎬 Watch It! —

A short YouTube video introduces vectors, resultant forces (the same idea as net forces), and how to add and subtract forces in two perpendicular directions. Kids answer three questions: what two things vectors include (magnitude and direction), what net forces are, and a worked example with an airplane (vertical net force, horizontal net force, overall net force). Visual learners hook in fast at this station because the video shows the arrows being added on screen, which makes the math click before kids see it on a worksheet.

📖 Read It! —

A one-page passage called "The Mystery of the Floating Balloon" frames the lesson around a balloon that hovers in midair, neither rising nor falling. The passage walks through balanced forces (equal in opposite directions, no change in motion), unbalanced forces (one side stronger, change in motion), net force (sum or difference of all forces, measured in newtons), free-body diagrams, and vectors (arrows showing magnitude and direction). Vocabulary is bolded throughout. Three multiple-choice questions follow, plus the vocab notes section. Comes in two reading levels (Dependent and Modified) plus a Spanish version.

🔬 Explore It! —

This is the heart of the lab. Three-part spring-scale investigation. Part 1: Kids attach spring scales to opposite sides of a small object on the table. One person pulls at 50 N, the other at 75 N from the opposite side. They observe direction of motion and calculate net force (25 N toward the 75 N side). Part 2: Both pull at exactly 50 N from opposite sides. The object doesn't move. Net force is zero. Balanced. Part 3: Two people pull from the SAME side, each with 50 N. The object accelerates fast. Net force is 100 N (forces add). Each part asks: was this balanced or unbalanced, and what was the net force?

💻 Research It! —

Students examine 8 reference cards: definitions of force, balanced forces, and unbalanced forces, a Common Forces table (applied force, normal force, gravity, friction, buoyancy, magnetism, with typical directions for each), and four real-life photo scenarios (a tug-of-war pull, a rock climber, a volleyball match, and a balanced-vs.-unbalanced car-pulling diagram). Five questions follow, asking kids to interpret balanced/unbalanced forces in each photo, calculate net force on the climber, and describe how forces act differently in horizontal vs. vertical directions.

Calculating Net Force Station Lab hands-on activity for TEKS 6.7B — 6th grade physical science

4 output stations: how students show what they learned

📋 Organize It! —

A matching card sort. Kids match six force diagrams with their correct net-force values. The values include 130 N right, 25 N left, 5 N left, 70 N right, 0 N (balanced), and 350 N down. Each diagram has multiple force vectors that students have to add (same direction) or subtract (opposite directions) to find the answer. The 0 N (balanced) card is the key catch: kids see two equal arrows pointing opposite ways and have to recognize that as zero, not as the size of one of the arrows. Easy to spot-check at a glance.

🎨 Illustrate It! —

Students draw two free-body diagrams: one of an object with balanced forces and one with unbalanced forces. They use vectors (arrows of different lengths) to represent each force, label each force by name (gravity, applied force, normal force, etc.), and show the net-force calculation underneath. The diagrams force kids to commit to the convention that arrow length equals force size, which makes adding and subtracting forces visual instead of just numeric. Even kids who say "I can't draw" surprise themselves here.

✍️ Write It! —

Three open-ended questions: how net force affects an object's motion, how to calculate net force when two people push a sled in the same direction with different strengths, and how to use a free-body diagram to show the forces on a bicycle going uphill (gravity down, normal force up, applied force from the rider, friction opposing motion). Forces kids to apply the indicators to brand-new scenarios. This is the writing practice middle schoolers need and rarely get in science class.

📝 Assess It! —

Eight multiple-choice and fill-in-the-paragraph questions tied to TEKS 6.7B vocabulary (balanced forces, unbalanced forces, net force, free-body diagram, vector). Includes what type of force is created when two unequal opposite forces act on an object (unbalanced), what a net force of zero means for motion (object is at rest or constant speed), and a rocket diagram where students calculate the net force from given thrust and gravity values. The fill-in paragraph weaves all five vocabulary words together using a hurricane scenario. If you're grading the lab, this is the easiest station to grade.

Bonus Challenge It! station for early finishers

🏆 Challenge It! —

Four optional extensions: write a 10-question quiz with answer key for classmates, run the PhET Forces and Motion Basics simulation manipulating mass and force values, create vector art (a large-scale paper-and-markers drawing with accurately scaled force arrows on a chosen object like a rocket or sailing boat), or work through a Math Connection set of real-world net-force calculations (sled with weights, parachute descent, etc.). Requires teacher approval before they start.

How this fits into a complete calculating net force unit

This Station Lab is the Explore day of our full Calculating Net Force Complete 5E Lesson for TEKS 6.7B. The complete two-week unit follows the 5E method of instruction and includes an Engage hook, the Calculating Net Force Station Lab for Explore, PowerPoint slides and interactive notebook pages for Explain, student choice projects to Elaborate, and an Evaluate assessment.

Most teachers grab the full 5E because the Station Lab lands hardest with the days around it. But if you just need a strong hands-on day on net force, balanced/unbalanced forces, and free-body diagrams, the Station Lab on its own does the job.

Two options

Full 5E Lesson $13.20 Get the 5E Lesson

Just the Station Lab $7.20 Get the Station Lab

Materials needed to teach calculating net force

Materials beyond what's in the download:

Two spring scales per station rotation. The standard 0-100 N classroom spring scales work great. If you only have one, you can run Parts 1 and 3 by having kids estimate the second pull, but two is much cleaner.
One small movable object (a wooden block, a small toy car, a binder, or a plastic container) per station. Anything with hooks or a way to attach the spring scales.
String or hooks if your object doesn't already have them, to attach the spring scales securely.
A clear flat work surface (table or smooth desk) where kids can pull from opposite sides without anything blocking the object.
Colored pencils or markers for the Illustrate It! station's free-body diagrams (different colors for different force types help readability).
Pencils and the printed answer sheets (included)
A device with internet for the Watch It! station

Standard covered: Texas TEKS 6.7B —

Calculate the net force on an object in a horizontal or vertical direction using diagrams and determine whether the forces are balanced or unbalanced. Supporting Standard.

See the full standard breakdown →

Grade level: 6th grade physical science

Time: One to two class periods (45–110 minutes total). Plan for two periods the first time you run a station lab.

Common student misconceptions this lab fixes

"If forces are balanced, then no force is acting on the object."
This is the big one. Sixth graders see balanced forces and assume zero forces. They confuse balanced (equal opposing forces) with absent (no forces). The Explore It! Part 2 fixes this directly. Both kids are pulling hard at exactly 50 N. The object doesn't move, but they can FEEL the rope under tension. Forces are clearly present, they just cancel each other out. The Read It! passage drives the same point home: gravity is pulling you down right now, but the floor is pushing you up with equal force. The forces are balanced, but they're not absent. The Organize It! card sort with the 0 N (balanced) diagram makes the rule explicit: balanced means equal and opposite, which gives zero NET force, not zero forces.
"Net force just means the biggest force."
Many 6th graders pick the largest individual force and call it the net force. The Watch It! video catches it with the airplane example: vertical lift might be 1000 N, gravity might be 1000 N, but the vertical net force is zero, not 1000 N. The Explore It! Part 1 makes it physical: 50 N vs. 75 N in opposite directions gives a net force of 25 N (the difference), not 75 N (the bigger one). The Organize It! card sort hits this multiple times. Kids who see arrows of size 100 and 30 in opposite directions and write "100 N" as the net force have to redo the matching when they get the wrong answer card. By the end, they're subtracting opposite-direction forces and adding same-direction forces correctly.
"If two forces are in the same direction, they don't add up. They just stay the same size."
This one shows up when kids see two arrows pointing the same way and freeze. The Explore It! Part 3 fixes it directly. Two kids pulling on the same side at 50 N each launches the object across the table, way faster than one 50 N pull would. They feel the difference in their muscles and see the difference in motion. The Read It! passage states the rule plainly: "if forces are in the same direction, we add them up." The Organize It! card sort then includes diagrams where same-direction arrows give totals of 130 N, 70 N, and 350 N, all calculated by addition. The handshake between the experiment, the rule, and the matching task locks the addition rule in.

What you get with this calculating net force activity

📷 Inside-the-product — add screenshot of Read It passage or sample answer sheet

When you buy the Station Lab, you get a single download with everything you need:

Print version at two reading levels (Dependent for on-grade, Modified for additional support) plus a Spanish Read It! passage
Digital version as PowerPoint files (works in Google Slides too) at both levels for 1:1 classrooms or Google Classroom
Teacher Directions and Answer Key for both versions, all keys included
Station task cards ready to print, laminate, and drop in baskets at each station
Reference cards for the Research It! station (force/balanced/unbalanced definitions, common forces table, photos of tug-of-war, rock climbing, volleyball, and a car force diagram)
Sort cards for the Organize It! station (six force diagrams plus six matching net-force values)
Student answer sheets for each level

Tips for teaching calculating net force in your 6th grade classroom

Two things make this lab go smoother the first time:

1. Calibrate the spring scales before class.

The Explore It! station depends on kids reading actual force values off spring scales. The first time I ran a similar setup, two of the spring scales had drifted (one read 8 N at rest, one read negative 5 N), and the groups using those scales got numbers that didn't match the predictions. Now I check each scale before class by zeroing it and pulling against a known weight (a 100 g mass = roughly 1 N). Takes 30 seconds per scale and saves a confused group later.

2. Tape down a clear pull zone on the table.

The 75 N pull in Part 1 launches the object pretty fast. Without a defined work area, the object skids off the table or whacks into someone's water bottle. Tape down a 24-inch by 36-inch rectangle of paper or a piece of cardboard on each station table. The object stays in the work area, kids pull more confidently because they know nothing's getting knocked over, and the visual boundary helps them estimate distance traveled (which connects to the next standard, 6.7C).

Get this calculating net force activity

Calculating Net Force Station Lab for 6th grade physical science — TEKS 6.7B

Buy the Station Lab — $7.20

Or if you want the full two-week experience with the Engage hook, Explain day, Elaborate extension, and Evaluate assessment all included:

Buy the full 5E Complete Lesson — $13.20

(Station Lab is included)

Frequently asked questions

What does TEKS 6.7B cover?

Texas TEKS 6.7B asks 6th grade students to calculate the net force on an object in a horizontal or vertical direction using diagrams and to determine whether forces are balanced or unbalanced. Students should be able to read a free-body diagram, add forces in the same direction, subtract forces in opposite directions, write the net-force value with a direction, and predict the object's motion. The standard pairs naturally with 6.7A (forces in the real world) and 6.7C (Newton's third law).

Is this kids' first time with vectors and free-body diagrams?

Yes for most 6th graders. They've heard "force" since elementary school, but representing forces with arrows of specific length and direction is brand new. The Watch It! video introduces vectors, the Read It! passage defines them, the Research It! reference cards model them in real photos, and the Illustrate It! station forces kids to draw their own. By the end, they can read a diagram and tell you the net force just by looking at the arrows.

How long does this calculating net force activity take?

One to two class periods (45 to 110 minutes total). The Explore It! station's three-part spring-scale investigation is the longest piece, so plan for two periods the first time you run a station lab. Once your class has the rotation routine down, most groups can finish all 8 stations in one period.

Do I need a lot of supplies for this?

Pretty light. Two spring scales per station rotation and one movable object per station. If your school has a physics kit, all the supplies are probably already in it. If not, spring scales run about $5-8 each from a science-supply vendor. Total cost for a class of 30 (5 station rotations): about $50-80, and the equipment is reusable for years.

Can I use this in a 1:1 digital classroom?

Yes. The full digital version (PowerPoint or Google Slides) works in 1:1 classrooms and Google Classroom. Students drag digital cards for the Organize It! sort and complete free-body diagrams on a digital canvas. The Explore It! spring-scale activity is harder to digitize, but the PhET Forces and Motion Basics simulation (free) is a great substitute and is also called out in the Challenge It! station.