FULL REVIEW
Full Review — Work and the Work–Energy Theorem — Foundational
Review the essential ideas, relationships, and problem-solving tools for Work and the Work–Energy Theorem.
TIME
45–60 minutes
BEST FOR
A complete topic review
FINISH WITH
A readiness check
After this full review, you'll be able to...
recall the essential ideas, apply them to representative problems, and determine what to study next.
Choose how you want to review
Course Alignment
This Physics Sensei Topic Review is an independent learning resource. Use it to reinforce key concepts, prepare for homework, or review before a quiz or exam.
Related Unit Review: If you need to review the complete unit material, review Work, Energy, and Power here →
RESOURCE: Physics Sensei Topic Review | TOPIC ID: MEC-U06-T01 | TOPIC: Work and the Work–Energy Theorem | PARENT UNIT: MEC-U06 — Work, Energy, and Power | COURSE LEVEL: Foundational
BEST USED ✓ After learning the topic ✓ Before starting homework ✓ Before a quiz or exam
Your Review Plan
Complete these six stages in order. Each stage builds on the previous one and prepares you for the final readiness check.
6 Stages • Approximately 45–60 minutes.
Warm-Up Check
Before you begin, take a moment to see what you already remember. Do not worry about getting everything right. This is only a starting point.
ACTIVITY 1
Recall Activity 1
Answer before revealing the response.
State the difference between positive and negative work in terms of energy transfer.
Reveal Answers
Positive work adds energy; negative work removes energy from the object.
Why it works: The sign describes the direction of energy transfer.
ACTIVITY 2
Recall Activity 2
Answer before revealing the response.
Can a large force do zero work? Give one situation where this happens.
Reveal Answers
Yes. For example, a force can be perpendicular to the displacement, or the object may not move.
Why it works: Work can be zero when there is no force component along the displacement.
ACTIVITY 3
Recall Activity 3
Answer before revealing the response.
A 25 N horizontal force moves an object 2 m forward. Find the work done by that force.
Reveal Answers
50 J. The force and displacement are parallel, so work is 25 × 2.
Why it works: For a parallel force, work equals force times displacement.
Ready to strengthen your understanding?
You've refreshed what you already know. Next, you'll reinforce the essential concepts that will help you solve problems with confidence. Need to see the learning path again?
Core Concepts
Let's rebuild the key ideas one step at a time. Focus on understanding the relationships before worrying about solving problems.
KEY CONCEPT 1
Work as Energy Transfer
A force does work when it acts through a displacement. The sign depends on whether the force component along the displacement points with or against the motion.
W = Fd
Example: A 30 N forward push through 4 m does +120 J of work when force and displacement are parallel.
Sensei note: Always compare force direction with displacement before assigning the sign.
KEY CONCEPT 2
The Work–Energy Theorem
The net work done by all forces equals the change in kinetic energy. This lets you connect the combined effect of forces directly to a change in motion.
Wnet = ΔK
Example: If net work is -18 J, kinetic energy decreases by 18 J.
Sensei note: Add the work from all relevant forces before using the theorem.
KEY CONCEPT 3
Kinetic Energy and Speed
Kinetic energy depends on mass and on the square of speed. Increasing speed therefore changes kinetic energy more rapidly than a simple one-to-one change.
K = ½mv²
Example: A 2 kg object moving at 3 m/s has 9 J of kinetic energy.
Sensei note: Because speed is squared, doubling speed makes kinetic energy four times as large.
Ready to apply these ideas?
You've reinforced the essential concepts. Now it's time to put them into practice by working through guided examples and building your problem-solving confidence. Need a quick reminder?
Guided Practice
Now it's time to apply what you've reviewed.
Work through each activity in order. The examples become gradually more challenging, and each one prepares you for the final readiness check.
PRACTICE 1
Worked Example
Calculate the work done by one force and explain its sign.
A 18 N push moves a crate 6 m forward. Find the work done by the push.
Reveal Answers
108 J, positive. The push is parallel to the displacement.
Why it works: Parallel force and displacement produce positive work.
PRACTICE 2
Guided Problem
Use net work to find the final kinetic energy.
A cart starts with 50 J of kinetic energy. The net work on it is +35 J. Find the final kinetic energy.
Reveal Answers
85 J. Add the +35 J net work to the initial 50 J.
Why it works: The theorem says net work equals the kinetic-energy change.
PRACTICE 3
Independent Problem
Use kinetic energy to connect mass and speed.
A 4 kg object moves at 5 m/s. Find its kinetic energy.
Reveal Answers
50 J. One-half times 4 kg times (5 m/s) squared gives 50 J.
Why it works: Kinetic energy is one-half mass times speed squared.
Ready to check your understanding?
You've practiced the essential skills with guidance. Now it's time to solve a few short problems on your own and confirm you're ready to move forward. Need a quick reminder?
Confidence Check
You've rebuilt the key ideas and practiced them with guidance. Now try these short questions on your own to check your understanding before moving on.
QUICK CHECK 1
Work Sign
Solve independently before checking the solution.
A force points opposite the displacement. What sign is the work done by that force?
Reveal Answers
Negative. The force opposes the displacement.
Why it works: Opposing force and displacement produce negative work.
QUICK CHECK 2
Work–Energy Update
Solve independently before checking the solution.
An object begins with 70 J of kinetic energy and experiences -20 J of net work. What is its final kinetic energy?
Reveal Answers
50 J. The net work removes 20 J from the initial 70 J.
Why it works: Negative net work decreases kinetic energy by the same amount.
QUICK CHECK 3
Kinetic Energy
Solve independently before checking the solution.
What happens to kinetic energy if speed doubles while mass stays constant?
Reveal Answers
It becomes four times as large.
Why it works: Kinetic energy depends on the square of speed.
How did it go?
You've checked your understanding. Take one final look at the essential ideas before deciding what to do next. Need a quick reminder?
Summary
Before moving on, take one final look at the most important ideas from this review.
KEY TAKEAWAY 1
Work Transfers Energy
Work is energy transferred by a force acting through displacement; its sign depends on direction.
KEY TAKEAWAY 2
Net Work Changes Motion
Net work equals the change in kinetic energy, providing a direct energy route from forces to motion.
KEY TAKEAWAY 3
Speed Matters Strongly
Kinetic energy grows with the square of speed, so speed changes have a strong energy effect.
MY ONE-SENTENCE SUMMARY
In my own words, the most important idea is:
____________________________________________
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