Levers

• A lever is a simple machine — a rigid bar that turns around a fixed point called the fulcrum.
• The force we apply is called the effort, and the weight we want to move is called the load.
• A seesaw, scissors, pliers, and a crowbar (nail-puller) are common examples of levers.
• A lever makes work easier by letting a smaller effort move a heavier load, when the effort is placed farther from the fulcrum than the load.
• On a balanced seesaw, if the effort is placed twice as far from the fulcrum as the load, only half as much effort force is needed to balance the load.

Level 1 - Core idea

Verbal: A lever is a rigid bar pivoting on a fulcrum, with effort applied at one point to move a load at another. Placing the effort farther from the fulcrum than the load makes lifting easier, needing less effort force.

Symbolic: effort x distance from fulcrum = load x distance from fulcrum (for balance)

Visual: On a seesaw, a lighter child sitting farther from the centre can balance a heavier child sitting closer to the centre.

Level 2 - NCERT anchor

NCERT Looking Around 5 links this to tools used at home and on farms, such as scissors, pliers, and crowbars, as everyday levers.

A load of 20 newtons sits 1 metre from the fulcrum of a lever. An effort is applied 2 metres from the fulcrum on the other side. What effort is needed to balance the load?

Step 1 - For balance: effort x effort-distance = load x load-distance.
Step 2 - Effort x 2 = 20 x 1, so effort x 2 = 20.
Step 3 - Effort = 20 / 2 = 10 newtons.
Answer: An effort of 10 newtons is needed to balance the 20 newton load.

Why is it easier to remove a stuck nail using a long-handled crowbar than by pulling it with your fingers?

Step 1 - The crowbar acts as a lever with a fulcrum near the nail.
Step 2 - Your hand applies effort far from the fulcrum, while the nail (load) is close to it.
Step 3 - Being far from the fulcrum lets a smaller effort move the load.
Answer: The crowbar's lever action lets you pull the nail with much less effort.

• What is the fixed pivot point of a lever called?
• What are the two forces called that act on a lever?
• Name two tools at home that work as levers.
• How does placing the effort farther from the fulcrum help?
• Stretch: If a load is 3 metres from the fulcrum and needs an effort placed 1 metre away, is the lever making the work easier or harder?

Revision tip: Picture a seesaw whenever you think about effort, load, and the fulcrum of a lever.

Open the Practice tab for graded questions on Levers.