Load Busters Unit • Lesson 1 Student Worksheet Page 1 of 2
Pick the best building materials and fix a broken skyscraper design.
Part 3 & 4
Use words from the Word Bank below
🔑 Word Bank • Material Properties:
Tension Strength (Holds pulling) Compression Strength (Holds crushing) Shear Strength (Resists sliding cuts)
Job 1: Strong cables hanging a bridge or holding a tall antenna Force: Tension (Pull)
Should the engineer choose Braided Steel Cables or Rigid Clay Bricks?
I choose Braided Steel Cables because steel has great so it will not snap when pulled.
Job 2: Thick ground pillars holding up 40 stories of heavy rooms Force: Compression (Push)
Should the engineer choose Reinforced Concrete Columns or Cardboard Tubes?
I choose Reinforced Concrete Columns because concrete has high so it will not crush under weight.
Job 3: Tough steel bolts pinning floor beams to corner columns Force: Shear (Slide)
Should the engineer choose Heavy Steel Fasteners or Plastic Glue Sticks?
I choose Heavy Steel Fasteners because they resist so the joint won't slice in half.
Be a Building Detective
What happened: During a windy storm, a tall 20-story building started to sway side to side and twist like a dishcloth! The columns started bending outward because there were no diagonal supports.
1. Which force made the building twist?
A) Torsion (Twisting force) B) Tension (Pulling force)
2. How can engineers fix the wobbling?
"To stop the twisting and swaying, the engineers should add diagonal X-braces because triangles _____________________________________."
Load Busters Unit • Lesson 1 Student Worksheet Page 2 of 2
3. Testing & Analysis
Required Lab Materials & Testing Apparatus (Class of 28 • 7 Teams) Accessible • Hands-On
Force Stations: Gridded foam blocks, rubber bands, yarn, paper strips, straws, weights, card deck, brads.
Playground Build: 400 craft sticks, low-temp glue guns or wood glue, cardstock gussets, string for swings, wax paper.
Test Rig: 5-gal bucket or hanging pan, S-hooks, digital hanging scale or calibrated iron weights, safety catch box.
Safety & Scales: Digital gram scales (0.1 g), metric rulers, ANSI Z87.1 safety goggles for all during test.
Load Busters Engineering Curriculum • Teacher Facilitation Guide Page 1 of 2
Strategies for Lower-Level Readers, ELL Learners, Safety Protocols & Scoring Rubrics
Facilitator Playbook 2/2
1. Sentence Starters & Word Banks
All lab sheets feature embedded sentence starters (e.g., "The legs bowed outward because...") and visual word banks. Striving writers focus on scientific reasoning without getting bogged down by blank writing spaces.
2. Multimodal Assessment
Accept sketches, physical hand gestures (showing push/compression vs pull/tension), or verbal explanations for students with reading barriers. Peer pairs allow stronger readers to read station steps aloud.
3. Step-by-Step Math Support
The strength ratio formula is broken into 3 clear steps on the Safety Lab Report (Step 1: Write weights → Step 2: Live ÷ Dead → Step 3: Match score to the 3-star safety rating scorecard).
× Misconception 1: "More glue makes the swing frame stronger."
Students apply heavy glue globs, thinking mass equals strength. Globs add dead weight and ruin the efficiency score.
✓ Fix: "Thin glue + corner gussets win."
Show that a thin glue smear with corner gusset plates holds 5× more shear stress while keeping dead weight under 60 g.
× Misconception 2: "Four vertical posts are enough for a swing set."
Students build straight rectangular legs without diagonals; swinging causes the frame to immediately tip sideways.
✓ Fix: "A-frame triangles cannot fold."
Demonstrate that triangular A-frames lock rigid. Cross-ties shorten unsupported post length, stopping buckling.
× Misconception 3: "A cracked playground model means I failed."
Students feel disappointed when their apparatus snaps under test weight, confusing destructive testing with failure.
✓ Fix: "Destructive testing keeps real kids safe!"
Frame test day as safety inspection. Finding the exact weak spot allows engineers to make Playground 2.0 child-safe.
Standardized Loading Steps
Safety Mandates
Force Lab (L1) 25%
Graded via Answer Key (10-pt rubric)
Playground Build (L2) 30%
Qualifies: ≥25 cm, ≤60 g, A-frame
Safety Report (L3) 25%
Data accuracy & failure diagnosis
Unit Test (L3) 20%
Playground Safety Unit Test (/50)
Load Busters Engineering Curriculum • Teacher Facilitation Guide Page 2 of 2
Tools: Playing card deck • Paper fasteners • Strips
What to do: Place a deck of cards flat on the desk. Put your palm on the top card and gently slide sideways. Notice how the card layers slide past each other like cards in a fan.
| Test Setup | What Action Was Done? | What Happened to the Layers? |
|---|---|---|
| 1. Free card deck | Pushed sideways | Cards slid past each other into a slope |
| 2. Strips held by 1 pin | Pulled opposite ways | Pin tilted and ripped through paper |
| 3. Strips glued with gusset | Pulled opposite ways | Reinforced joint stayed solid |
Draw Sliding Cards:
[ Draw cards slanting sideways → ]
Sentence Starter: "Shear happens when sideways forces push in opposite directions, like ____________________________________________________."
Tools: Foam beam with drawn squares • Sponge
What to do: Hold the bottom of the foam beam tightly against the table. Twist the top with your other hand. Watch how the square grid lines change into slanted diamond shapes!
| Amount of Twist | Grid Shape Change | How Did the Foam Feel? |
|---|---|---|
| Small Twist (1/4 turn) | Squares tilted a little | Gentle tightness in the middle |
| Big Twist (1/2 turn) | Squares turned into diamonds | Very tight, wanted to snap back |
Draw Twisting Diamonds:
[ Draw twisted diagonal diamonds ◊ ]
Sentence Starter: "When a structure is twisted, square frames warp into diamonds, which is why diagonal braces are needed."
Complete these two sentences to plan your tower design:
1. "The biggest force threat to our tall tower when heavy weights are placed on top is [ Tension / Compression / Torsion ]."
2. "To make our tower strong and stop it from twisting or bending, our team will add ____________________________________________________________________."
Load Busters • Lesson 1 Station Handout Page 2 of 2
Load Busters Curriculum • Master Answer Key Page 1 of 2
Answer key for Parts 3 & 4 plus quick teacher grading rubric.
Master Key 2/2
Word Bank Key
Job 1: Hanging Cables Force: Tension
Correct Selection: Braided Steel Cables • Property: Tension Strength (holds pulling without snapping).
Job 2: Ground Pillars Force: Compression
Correct Selection: Reinforced Concrete Columns • Property: Compression Strength (holds crushing downward weight).
Job 3: Fasteners & Bolts Force: Shear
Correct Selection: Heavy Steel Fasteners • Property: Shear Strength (resists sliding cuts between beam joints).
Problem Solving
Question 1: Force that made it twist
✓ Correct: A) Torsion (Twisting force)
Swirling wind puts unequal pressure on building walls, creating rotational torque.
Question 2: How to fix the wobbling
"...add diagonal X-braces because triangles cannot bend or fold without breaking, locking the corners rigid."
Formative Assessment
| Assignment Section | Points | Mastery Look-Fors |
|---|---|---|
| Part 1: 4 Force Models | 4 pts | Accurately identifies stretching, squeezing, tilting, and twisting actions. |
| Part 2: Dead vs. Live Loads | 2 pts | Correctly sorts moving contents (Live) vs permanent structure (Dead). |
| Part 3: Material Chooser | 2 pts | Matches tension strength to cables and compression strength to columns. |
| Part 4: Wobbling Solution | 2 pts | Identifies torsion and explains that triangles lock square corners rigid. |
Differentiation Note: For emerging bilingual students, accept verbal explanations or hand demonstrations of tension/compression forces during station checks.
Load Busters Curriculum • Master Answer Key Page 2 of 2
Load Busters • Playground Engineering Lexicon Page 1 of 2
Unit Reference Playground Engineering Lexicon
Part 2 • Framing & Failure
Key terms for building stable apparatus, preventing sway, and analyzing break points.
Pages 1 & 2
The Anatomy of Playground Apparatus
Support Post (Column) Vertical / Angled
A vertical or angled timber/metal post carrying compressive weight from monkey bars, slides, or swing beams straight down to the foundation.
Crossbeam Horizontal Span
A horizontal member spanning between posts that holds swings or climbing rungs, experiencing compression along its top and tension along its bottom.
A-Frame Truss Triangular End Frame
Two angled legs connected by a horizontal tie bar to form a rigid triangle. Triangles cannot change shape without breaking, preventing swing sets from toppling.
Diagonal Cross-Bracing Anti-Sway Tie
Diagonal members (such as X-braces) fastened across rectangular frames to stop side-to-side sway and frame twisting (shear & torsion).
Gusset Plate (Joint Bracket) Corner Reinforcement
A flat plate (steel bracket in real parks, cardboard triangle in student models) glued or bolted across a joint where posts and crossbeams meet to stop shear slicing.
Pinpointing Hazards & Flaws
Post Buckling
A sudden sideways bowing or snap of a slender support post under compressive live loads before the wood crushes.
Fix: Add cross-ties to shorten post height.
Failure Point
The exact physical component or maximum load where playground equipment gives way, tears, or cracks.
Rule: Weakest joint breaks first!
Strength Ratio
A safety ratio comparing live play weight held to the structure's own dead weight:
Score = Live Load ÷ Dead Load
Quick Check: Connect the Playground Part to its Force
• Swing Chains: Tension (pulling downward)
• Support Posts: Compression (squeezing downward)
• Crossbeam Bracket: Shear (slicing across joint)
• Swivel Tire Swing: Torsion (twisting along axis)
• A-Frame Legs: Triangulated stability against sway
• Gusset Plate: Reinforcing plate against shear tears
Load Busters • Playground Engineering Lexicon Page 2 of 2
Draft your side frame elevation directly on this grid. You will lay craft sticks right over it to build!
Grid: 1 square = 1 cm
Ground Footprint: ≤ 20×20 cm Minimum Height: 25 cm Top Beam Span: 15–20 cm
0 cm (Ground Level) 10 cm (Lower Cross-Tie) 20 cm (Mid-Brace / Platform) 25+ cm (Top Beam • Load Hook)
[ Draw 1 Side Frame Elevation of Your Playground Structure ] Sketch A-frame legs, top crossbeam, and diagonal braces. Build under wax paper!
A-Frame Legs (Compression) ← Triangular Gusset Plates at Top Corners → Diagonal Ties (Shear/Torsion)
Inspect before test day crush testing!
Height: Structure is at least 25 cm tall. Footprint: Base fits inside 20×20 cm test area. Load Zone: Top beam/deck has secure test hook.
Dead Weight: Weighs under 60.0 grams. Gusset Joints: Corners reinforced against shear slicing. Triangles: Diagonal bracing stops sway and twisting.
Playground Safety Inspector Sign-Off: Approved for live load crush testing!
Inspector Signature:
Empty Model Weight: g
Load Busters • Playground Engineering Blueprint Guide Page 2 of 2
Timeline
Step 1
Draft your 1:1 elevation on paper first.
Step 2
Glue craft sticks to form 2 matching side frames.
Step 3
Connect frames with top crossbeam & X-braces.
Step 4
Add corner gussets. Weigh (≤ 60 g) & let dry!
Safety Protocol: Wear goggles • Thin, even glue smears dry stronger and lighter than thick blobs!
Sketch the Broken Apparatus:
[ Draw your broken playground model & circle the exact failure point! ]
Complete the sentences to explain your safety upgrades
1. Eliminating the Failure Weakness:
"To keep kids safe and stop the playground structure from failing at that same spot, our team will ________________________________________________________________________________________________."
2. Strengthening Against Specific Forces:
"We will add [ cardboard gusset plates / diagonal X-braces / bundled A-frame legs ] to protect against the force of ________________________________________________________________________."
3. Protecting Children While Keeping Weight Low:
"Our structure will stay light (under 60 g dead weight) because we will place triangles only where ________________________________________________________________________________________________."
Engineering Team Safety Sign-Off All partners approve the Playground 2.0 blueprint
Safety Lead:
Chief Builder:
Load Busters • Playground Safety Lab Report Page 2 of 2
⭐⭐ 41 - 70: Community Park Grade
⭐⭐⭐ 71+: Superpark Engineering!
A lightweight design with strong triangulated joints earns the top engineering score!
Next Iteration
1. Weak Spot
Name the exact joint, beam, or post that failed first.
2. What to Add
Add corner gussets, lap splices, or diagonal ties to stop sway.
3. Keep it Light
Target reinforcements specifically where forces concentrate.
Now complete Part 4 & 5 on your Playground Safety Lab Report to design Playground 2.0!
Unit Assessment Analysis & Engineering Design
Part 3 & 4 • 20 Points
Classify playground loads and troubleshoot an apparatus failure scenario.
Page 2 of 2
Classification & Analysis
Playground Design Scenario: City engineers are inspecting a school playground for safety. For each item below, check whether it is a Dead Load or a Live Load (1 pt each = 5 pts).
| Playground Structure Element / Force | Dead Load (DL) | Live Load (LL) |
|---|---|---|
| 1. Heavy cedar timber posts and steel top swing beam | ||
| 2. 20 middle school students running, climbing, and jumping on deck | ||
| 3. Molded plastic spiral tube slide and aluminum steps | ||
| 4. Sudden 45 mph thunderstorm wind gusts pushing against canopy | ||
| 5. Maintenance technician standing on roof with heavy repair tools |
6. Safety Engineering Reasoning: Why must playground builders plan for the combined total load (Dead Load + maximum Live Load with a 4× safety factor)? What happens if they only calculate the empty structure weight? (5 pts)
Safety Redesign
Testing Observation: "During destructive load testing, Team Park's 25 cm swing set model held 400 grams easily. At 550 grams, the long slender vertical legs bowed outward in a sharp C-curve and snapped sideways under compressive load. The top crossbeam and swing chains remained intact, but the legs collapsed because there were no horizontal tie bars between the legs."
7. What specific failure mode occurred when the slender legs bowed outward under compression? (3 pts)
A) Leg Buckling
B) Joint Shear Tear
C) Frame Torsion Twist
8. Safety Redesign Plan: How should Team Park redesign their swing frame legs to stop this buckling failure? Name the specific framing technique and explain why it keeps children safe without adding too much dead weight. (7 pts)
Load Busters • Playground Safety Unit Assessment Page 2 of 2
Key Insight: Triangles are the only polygon with inherently locked geometry.
Grading Strategy for Page 1: Questions 1–6 evaluate core foundational understanding. If students struggle with forces, recommend re-visiting the Playground Forces Vocabulary Guide before attempting the redesign.
Load Busters • Playground Safety Answer Key Page 1 of 2
Teacher Key Grading Guide • Load Analysis & Rubrics
Part 3 & 4: 20 Points
Solutions for playground load classification and full-credit criteria for safety redesign.
Page 2 of 2
Table (5 pts) • Reasoning (5 pts)
| Playground Structure Element / Force | Correct Answer | Engineering Explanation |
|---|---|---|
| 1. Cedar timber posts and top swing beam | Dead Load (DL) | Permanent physical materials of the equipment itself. |
| 2. 20 students climbing and jumping | Live Load (LL) | Dynamic, variable weight of users moving on and off. |
| 3. Molded plastic spiral slide tube | Dead Load (DL) | Permanent fixed component attached 24/7 to the tower. |
| 4. 45 mph thunderstorm wind gusts | Live Load (LL) | Dynamic, variable environmental force pushing on canopy. |
| 5. Maintenance technician with tools | Live Load (LL) | Temporary worker and equipment weight during repair. |
6. Safety Engineering Reasoning Rubric (5 Points):
Full Credit (5 Pts): Student explains that equipment must support total load = Dead Load + maximum Live Load with a safety factor (typically 4×). If engineers ignore live loads or dynamic jumping forces, the active children will overload timber posts or bolts, causing post buckling, bracket shear, or catastrophic collapse leading to child injury.
Partial Credit (2–4 Pts): Student notes that the playground will break under too many kids, but does not distinguish permanent dead weight from variable live/dynamic forces or safety factors.
Diagnosis (3 pts) • Redesign (7 pts)
7. Failure Mode: A) Leg Buckling (Compressive bowing/snapping of slender vertical legs)
3 Points
8. Safety Redesign Scoring Rubric (7 Points Total):
| Score | Criteria Met | Exemplar Indicators |
|---|---|---|
| Full Credit | ||
| (6–7 Pts) | Identifies adding horizontal cross-ties or A-frame trusses between the legs; clearly explains that cutting the unsupported leg length in half prevents compressive buckling without adding excessive dead weight. | "Add horizontal cross-tie bars between the legs to form an A-frame triangle. This cuts the unsupported post height in half, stopping the wood from bowing outward under compression while keeping dead weight low." |
| Partial Credit | ||
| (3–5 Pts) | Suggests adding braces or supports, but offers vague reasoning (e.g. "make legs thicker" or "add more sticks") without explaining buckling or triangle geometry. | "Add sticks between the legs so they won't bend." (Identifies location, lacks specific engineering mechanism). |
| Minimal Credit | ||
| (1–2 Pts) | Only suggests piling on hot glue or doubling all wood, which unnecessarily inflates Dead Load without solving structural geometry flaws. | "Put thick layers of hot glue all over the legs." |
Score Conversion: 45–50 pts = Exceeds Mastery (A) • 40–44 pts = Proficient (B) • 35–39 pts = Developing (C)
NGSS MS-ETS1-2, MS-ETS1-3, MS-PS2-2
Load Busters • Playground Safety Answer Key Page 2 of 2
