Momentum, Work, and Simple Machines
This lesson pulls together three related ideas: momentum (the motion an object carries), work (using force to move something), and simple machines (tools that make work easier). Each has a clean definition, and together they round out mechanics on the test.
Momentum
Momentum is a measure of how hard it is to stop a moving object. It depends on mass and velocity: \[ \text{momentum} = \text{mass} \times \text{velocity}. \] A heavy truck moving slowly can have as much momentum as a light car moving fast. In a collision, momentum is conserved — the total momentum before equals the total after. That is why a moving ball transfers its momentum when it hits a still ball.
Work
Work, in physics, means using a force to move an object a distance: \[ \text{work} = \text{force} \times \text{distance}. \] Lifting a box does work; simply holding it still does not, because nothing moves. If you push with \(10\) newtons over \(3\) meters, you do \[ 10 \times 3 = 30 \text{ joules} \] of work. Work is how force actually transfers energy to an object.
Simple Machines
Simple machines make work easier by changing the size or direction of a force. There are six: the lever, the pulley, the wheel and axle, the inclined plane, the wedge, and the screw. A ramp (inclined plane) lets you raise a heavy object with less force by pushing it over a longer distance. A lever lets you lift a big load with a small effort. Machines do not reduce the total work — they trade more distance for less force, which is called mechanical advantage.
Watch: A Short Video Lesson
CodeLucky walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
A Routine for These Questions
- Momentum = mass times velocity; it is conserved in collisions.
- Work = force times distance; no movement means no work.
- Simple machines trade distance for force (mechanical advantage).
- Know the six: lever, pulley, wheel and axle, inclined plane, wedge, screw.
Practice
- Write the formula for momentum.
- A \(2\) kg ball moves at \(5\) m/s. What is its momentum?
- Write the formula for work.
- You push a cart with \(20\) N over \(4\) m. How much work is done?
- Does holding a heavy box still do any work?
- Name two simple machines.
Answers
- \(\text{momentum} = \text{mass} \times \text{velocity}\).
- \(2 \times 5 = 10\) (kg m/s).
- \(\text{work} = \text{force} \times \text{distance}\).
- \(20 \times 4 = 80 \text{ joules}\).
- No — nothing moves, so no work is done.
- Any two of: lever, pulley, wheel and axle, inclined plane, wedge, screw.
Where This Fits in Your Science Prep
These ideas build on forces and energy, since work is how force transfers energy. See all topics on the Science Topics Hub.
Recommended Prep Books
These study guides and practice books help you keep building momentum as you prepare:
Related to This Article
More math articles
- Top 10 Tips for Managing Time Effectively on the SAT Math
- How to Convert, Compare, Add, and Subtract Mixed Customary Units?
- Parallel and Perpendicular Lines for 4th Grade
- The Best Algebra 1 Book for Nebraska Students
- Vermont SBAC Grade 6 Math Free Worksheets: Free Printable PDF Worksheets with Worked Solutions
- The Best Grade 4 ELA Practice Tests for Georgia Students
- Top 10 4th Grade MEAP Math Practice Questions
- 10 Most Common CBEST Math Questions
- From Cells to Organisms: Levels of Organization
- Rounding Numbers Practice — Free Interactive Drills
What people say about "Momentum, Work, and Simple Machines - Effortless Math"?
No one replied yet.