Loads and Structures: Tension, Compression and Safety Factors

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Career and Technical Education · Engineering / Robotics / Industrial Technology
SP-ENGR-006 · Free to print and use in your classroom · substituteplans.com
Page 2
Loads and Structures: Tension, Compression
and Safety Factors
Career and Technical Education · Engineering / Robotics / Industrial Technology · Grades 9-12 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). No other prep is needed.
Technology
None. Calculators are optional.
Student
independence
High. Students work alone, then compare with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Calculators (optional)
Goal for today: Students will classify forces as tension or compression, distinguish dead from live loads, and calculate
total load, safety factor, support reactions and footing pressure.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ This is a reading and calculation lesson. Students must NOT use any tools, weights or building materials
today.
☐ On the board write: Total load = dead load + live load. Safety factor = failure load ÷ expected load. Pressure
= force ÷ area.
☐ Keep the answer key (page after the worksheet) on your desk.
Say this to start
Good morning! Today you will think like a structural engineer. Structures such as bridges, buildings and shelves all
have to carry weight without failing. You will learn the words engineers use for the forces involved and do some
calculations to see how much weight a structure can safely hold. It is all on paper, and the passage explains each idea.

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Career and Technical Education · Engineering / Robotics / Industrial Technology
SP-ENGR-006 · Free to print and use in your classroom · substituteplans.com
Page 3
Run of show
Minutes
What you do
What students do
0–5
Take attendance the way the school requires. Hand out the
worksheet.
Settle in and take out a pencil.
5–15
Read the passage aloud slowly. Pause after each bold term
and ask, “What is an everyday example?”
Listen and underline each bold term.
15–22
Tell students to complete the word-bank fill-ins (questions
1–6).
Fill in each blank with a word from the box.
22–40
Tell students to complete questions 7–13 in the work
boxes. Remind them to include units.
Calculate loads, safety factors, support
reactions and pressure.
40–47
Tell students to answer questions 14–16.
Answer a multiple-choice, a true/false and a
short question.
47–50
Collect all worksheets and put them in a stack for the
teacher.
Hand in the worksheet.
If things go wrong
• If students mix up tension and compression, tell them: tension pulls things apart (like a rope), compression
squeezes them together (like a column).
• If a student says they cannot do the support-reaction questions, point to the formulas in the passage and do
the first number substitution together.
• If a student wants to build a model, remind them that today is paper only and no materials or tools are to be
used.
• If a student finishes early, check units on every answer, then use the early finisher list.
Early finishers
• Sketch a simple bridge and label two parts as tension or compression.
• Write one real-life example of a dead load and one of a live load for your home.
Support and challenge
• Support: Let students use calculators and complete questions 1–8 and 14–16 only.
• Challenge: Ask students to find the left and right support forces when a 300 lb load sits 2 ft from the left end
of an 8 ft beam (225 lb and 75 lb).
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:

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Career and Technical Education · Engineering / Robotics / Industrial Technology
SP-ENGR-006 · Free to print and use in your classroom · substituteplans.com
Page 4
Anything the teacher should know: