Science · Grade 5 · Forces and Simple Machines · Term 1

Screws and Wedges

Students will investigate how screws and wedges function as simple machines to apply force or hold objects together.

• Ontario Curriculum Expectations
• 3-5-ETS1-1

About This Topic

Screws and wedges serve as simple machines that apply force efficiently. Students investigate how a screw functions as an inclined plane wrapped around a cylinder, converting rotational motion into linear force for fastening wood or metal. Wedges, with two sloping sides, split materials or hold objects in place by directing force inward. These concepts align with Ontario Grade 5 expectations for understanding forces and mechanical advantage.

This topic fits within the Forces and Simple Machines unit, where students compare screws and wedges to inclined planes and other machines. They analyze how thread pitch on screws affects fastening effort and how wedge angle influences splitting power. Key questions guide inquiry: explaining screw mechanics, comparing wedges to ramps, and designing tools using these principles. This develops engineering skills per standard 3-5-ETS1-1.

Active learning shines here because students test real materials like bolts in wood blocks or sharpened pencils as wedges. Hands-on trials reveal force relationships directly, correct misconceptions through trial and error, and spark creative designs that make abstract physics tangible and engaging.

Key Questions

1. Explain how a screw uses an inclined plane to create a strong fastening force.
2. Compare the function of a wedge to that of an inclined plane.
3. Design a tool that incorporates the principles of a screw or a wedge.

Learning Objectives

• Explain how the inclined plane principle is applied in a screw to create a fastening force.
• Compare the function of a wedge in splitting or holding objects to the function of an inclined plane.
• Design a simple tool that utilizes the mechanical advantage of either a screw or a wedge to perform a specific task.

Before You Start

Introduction to Simple Machines

Why: Students need a basic understanding of what simple machines are and how they make work easier before investigating specific types like screws and wedges.

Forces and Motion

Why: Understanding concepts like push, pull, and direction of force is foundational to grasping how screws and wedges apply or direct force.

Key Vocabulary

Inclined Plane	A simple machine consisting of a flat supporting surface tilted at an angle, with one end higher than the other. It is used to move heavy objects up or down.
Screw	A simple machine consisting of an inclined plane wrapped around a cylinder or cone. It is used to fasten materials together or lift objects.
Wedge	A simple machine that tapers to a thin edge. It is used to split, lift, or hold objects by directing force to the sides.
Mechanical Advantage	The factor by which a simple machine increases the input force to produce a greater output force. It makes work easier.

Watch Out for These Misconceptions

Common Misconception

A screw works like a nail by just pushing straight in.

What to Teach Instead

Screws use a wrapped inclined plane to gradually apply force through rotation. Hands-on fastening trials with nails versus screws let students feel the difference in effort and see threads grip, building accurate mental models.

Common Misconception

A wedge is the same as an inclined plane or ramp.

What to Teach Instead

Wedges have two inclined planes meeting at a thin edge to split or hold, unlike single-sided ramps that lift. Active comparisons with models help students observe force application and correct this through direct manipulation.

Common Misconception

Steeper screw threads always make fastening easier.

What to Teach Instead

Finer threads require more turns but less force per turn. Testing multiple screws reveals trade-offs, and group discussions clarify ideal designs for specific tasks.

Active Learning Ideas

Stations Rotation: Screw Thread Testing

Prepare stations with screws of varying thread pitches and wood blocks. Students twist screws into blocks, measure force with spring scales, and record turns needed. Rotate groups every 10 minutes to compare results and discuss patterns.

45 min·Small Groups

Pairs Challenge: Wedge Splitting

Provide soft materials like clay or foam and wedges of different angles. Pairs push wedges to split samples, note effort required, and sketch angle-force relationships. Conclude with predictions tested on new materials.

30 min·Pairs

Whole Class Design: Custom Fastener

Brainstorm needs for a screw or wedge tool, then prototype using craft sticks, foil, and glue. Test prototypes on target materials and refine based on class feedback.

50 min·Whole Class

Individual Exploration: Ramp to Wedge

Students build paper ramps, then fold into wedges. Test pushing blocks up ramps versus splitting with wedges, journal observations on force direction.

25 min·Individual

Real-World Connections

• Carpenters use screws extensively to join pieces of wood for building furniture, decks, and houses, relying on the screw's ability to create a strong, secure fastening.
• Chefs use wedges in the form of knives to slice and dice ingredients, applying force to split food items like onions or potatoes efficiently.
• Engineers design bottle caps using screw threads to create a tight seal, preserving food and beverages, and also design wedges for splitting logs for firewood or in construction.

Assessment Ideas

Quick Check

Present students with images of various objects (e.g., a bolt, a knife, a ramp, a doorstop). Ask them to identify which objects use the principles of a screw or a wedge and briefly explain why.

Exit Ticket

On an index card, ask students to draw a simple diagram of either a screw or a wedge. Then, have them write one sentence explaining how their chosen simple machine helps to do work.

Discussion Prompt

Pose the question: 'How is a screw different from a simple ramp, even though both use the principle of an inclined plane?' Facilitate a class discussion where students share their ideas about rotational versus linear motion and fastening force.

Frequently Asked Questions

How do screws use inclined planes to fasten?

A screw wraps an inclined plane around a cylinder, so turning it moves the plane along the shaft. This spreads force over many small steps, reducing effort compared to hammering. Students grasp this best by unrolling paper into a screw model and simulating rotation on a dowel.

What is the main difference between a wedge and an inclined plane?

An inclined plane lifts objects gradually with one slope, while a wedge uses two slopes to push materials apart or lock them. Wedges transform sideways force into separation. Classroom demos with doorstops versus ramps highlight this distinction clearly.

How can active learning help teach screws and wedges?

Active approaches like building and testing prototypes engage kinesthetic learners and reveal principles through experience. Students twisting screws or chiseling with wedges measure forces firsthand, discuss failures, and iterate designs. This builds deeper understanding than diagrams alone, fostering problem-solving skills essential for engineering.

How to design a simple machine tool with screws or wedges?

Start with a problem like securing loose parts, then sketch screw or wedge solutions. Prototype affordably with recyclables, test mechanical advantage, and refine. Rubrics assess force efficiency and creativity, aligning with curriculum design expectations.