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An overview of how machines make work easier by changing force or direction.
Could you lift a heavy car with just one hand? It sounds like a superpower, but with the right tool, it is actually basic physics!
Quick Check
If you push against a brick wall as hard as you can but the wall does not move, have you done 'work' in the scientific sense?
Answer
No, because the distance moved is zero, and .
There are six classic simple machines that help us every day: 1. Lever: A stiff bar that pivots on a point called a fulcrum (like a seesaw). 2. Wheel and Axle: A circular frame (wheel) revolving around a central shaft (axle). 3. Pulley: A wheel with a groove for a rope that changes the direction of a pull. 4. Inclined Plane: A flat, sloped surface (a ramp). 5. Wedge: Two inclined planes joined back-to-back, used to split things apart (like an axe). 6. Screw: An inclined plane wrapped around a cylinder.
Imagine you need to lift a box into a truck. 1. You could lift it straight up (high force, short distance). 2. You could push it up a long ramp (low force, long distance). In both cases, the total work () is the same, but the ramp makes it feel easier because you don't have to push as hard at any one moment.
Quick Check
Which simple machine consists of a ramp wrapped around a central pole?
Answer
The screw.
The 'magic' of simple machines is called Mechanical Advantage (). This is a measure of how much a machine multiplies your input force. If a machine has an of , it means you only need to provide half the force normally required. However, there is always a trade-off: to use less force, you must apply that force over a longer distance. This is why a long, gentle ramp is easier to climb than a short, steep one—you walk further, but your legs don't have to work as hard per step!
Suppose you use a lever with a Mechanical Advantage of to lift a heavy rock that weighs . 1. Identify the : . 2. Use the formula: . 3. Calculate: . 4. Result: You only need to push with of force to lift a rock!
What is the scientific formula for Work?
If a machine allows you to lift a heavy object using very little force, what must be true about the distance you move?
A simple machine reduces the total amount of work required to complete a task.
Review Tomorrow
In 24 hours, try to name all six simple machines and find one example of each in your kitchen or garage.
Practice Activity
Look at a pair of scissors. Can you identify the two different simple machines that work together to make them work? (Hint: Look for a pivot and a sharp edge!)