Leversclasses 1–3.

Three bars. Same parts: fulcrum, effort, and load. The class is which part sits between the other two. Slide the arms and watch the force change.

Effort armLoad arm Mechanical advantage. A bigger number means less effort for the same load.

Setting the levers on the bench…

Lesson Shop / engineering: levers (classes 1–3)

All three classes stay on the bench. Click a bar to select it. Drag to look.

03 Bench Shop / engineering: levers (classes 1–3)

Move the arms.

The load stays 10 lb. Slide the effort or the load. Mechanical advantage is the effort arm divided by the load arm.

Effort arm — Load arm —

What a lever is for

Force or reach

A lever is a bar on a fulcrum. You apply the effort. The load is what you want to move.

Class 1 can go either way. Class 2 always multiplies force. Class 3 always multiplies distance.

First class: the fulcrum is in the middle. Second class: the load is in the middle. Third class: the effort is in the middle. You do not leave this page to compare them. All three bars stay in the view.

Try this

On class 1, slide the load toward the fulcrum. The effort force should fall. On class 2, try to make the advantage less than 1. You cannot. On class 3, the effort is always more than 10 lb.

04 Shop floor Ten minutes at the bench

Name thethree classes.

Use this page next to a meter stick, a pivot, and a weight. The classroom use is the lever class, and the force tradeoff that comes with it.

04.1

Learning objectives

Point to the fulcrum, the effort, and the load.
Say which part is between the other two for classes 1, 2, and 3.
Compute mechanical advantage as effort arm / load arm.
State the tradeoff: more advantage means less effort and less movement at the load.

04.2

Classroom loop

Cover the readout. Students name the middle part on each bar.
Class 1: move the load closer to the fulcrum. Record the new effort.
Class 2: predict the effort, then check. It stays under 10 lb.
Class 3: name a tool that reaches farther than the hand moves.

04.3

Shop examples

Class 1: crowbar, seesaw, pliers. Class 2: wheelbarrow, nutcracker, bottle opener. Class 3: tweezers, fishing rod, forearm. This model leaves out friction and the bend of a real bar.