Key Takeaways
- The Mechanical Comprehension Test is adaptive and fast, with up to 40 questions in 15 minutes.
- Focus first on force, motion, work, friction, levers, pulleys, gears, and mechanical advantage.
- Many SIFT mechanical questions are qualitative, so you often need the relationship more than heavy computation.
- When a machine reduces effort, it usually trades for more distance, more time, or both.
- Draw a simple sketch when a problem feels confusing; a clean picture often solves it faster than staring at the wording.
Last updated: March 2026
Forces, Work, and Simple Machines
The Mechanical Comprehension Test (MCT) is adaptive and gives you up to 40 questions in 15 minutes. That means you need conceptual speed, not just memory.
Core Ideas To Know Cold
| Concept | Key Idea |
|---|---|
| Force | A push or pull that can change motion |
| Mass | Amount of matter in an object |
| Weight | Force of gravity acting on mass |
| Work | Force applied over distance |
| Friction | Force that resists motion between surfaces |
| Mechanical advantage | How much a machine multiplies force |
Work and Mechanical Advantage
Machines do not create energy. They make work easier by changing:
- the amount of force
- the distance moved
- the direction of the force
If a pulley or lever lets you use less force, you usually pull farther.
Levers
| Lever Class | Fulcrum Position | Example |
|---|---|---|
| First-class | Fulcrum between effort and load | Seesaw, crowbar |
| Second-class | Load between fulcrum and effort | Wheelbarrow |
| Third-class | Effort between fulcrum and load | Tweezers, human forearm |
Lever Rule
The farther your effort is from the fulcrum, the more leverage you get.
Pulleys
| Pulley Setup | Effect |
|---|---|
| Single fixed pulley | Changes direction only |
| Single movable pulley | Reduces effort required |
| Multiple pulleys | Greater mechanical advantage |
Gears
Two reliable gear rules:
- Adjacent gears rotate in opposite directions.
- A small gear driving a large gear increases torque but decreases speed.
Friction and Motion
| Situation | What Usually Happens |
|---|---|
| More friction | Harder to slide, better traction |
| Less friction | Easier to slide, less grip |
| More mass | More resistance to changes in motion |
Fast Solve Habit
When you see a machine question, ask:
- What is the load?
- Where is the effort applied?
- What is the pivot or support point?
- Is the machine trading force for distance?
Those four questions solve a large share of SIFT mechanical items.
Test Your Knowledge
If you move the effort farther from the fulcrum on a lever, what usually happens?
A
B
C
D
Test Your Knowledge
What is the main benefit of a single fixed pulley?
A
B
C
D
Test Your Knowledge
If a small gear drives a larger gear, what is the usual result?
A
B
C
D