mechanical · 30 minutes · Official OETT Aligned
Levers & Sharing a Load
How distance from the pivot changes the result
What to know
- fulcrum: the pivot point
- torque or moment: turning effect
- types of levers
- how supports share weight
A small force far from the pivot can balance a larger force closer to it.
The core rule
Turning effect = force × the shortest distance from the pivot to the line of the force. Equal turning effects in opposite directions balance.
The pivot is called the fulcrum. The turning effect is called torque or moment. For a level lever with downward forces, multiply each force by its distance from the pivot. The side with the larger result drops. On a beam with two supports, a load closer to one support puts more weight on that support.
Worked examples
Example 1: easy
40 lb at 4 ft creates 160 lb·ft.
- The force is 40 lb and its distance from the pivot is 4 ft.
- Multiply: 40 × 4 = 160 lb·ft of turning effect.
Turning effect depends on force and distance together.
Example 2: medium
A 60-lb force 3 ft from a pivot balances 90 lb at 2 ft.
- Left side: 60 × 3 = 180 lb·ft.
- Right side: 90 × 2 = 180 lb·ft. The two sides balance.
Different forces can balance when their force × distance results match.
Example 3: hard
A 300-lb load sits one-quarter of the way from support A to support B. How much does each support carry?
- The 300-lb load is one-quarter of the way from support A to support B.
- A carries three-quarters: 300 × 3/4 = 225 lb. B carries the remaining 75 lb.
The nearer support carries more. Together they still carry 300 lb.
Common mistakes
The side with the larger force always drops.
Compare force × distance on both sides. Distance can make the smaller force win.
Put it into practice
Use guided explanations, check your answers, and try a new variation.