⚙️ Simple Machines: Lifting with Less Force

Can a tiny penguin lift a huge rock? With the right tool, yes! Today we meet the simple machines that make our work easier.

We have five helpers: the lever, the pulley, the inclined plane (a ramp), the wheel and axle and the screw. Simple machines change the size or the direction of a force.

First, the lever. A plank and a pivot (also called a fulcrum) are enough. At one end of the plank there is the load, and we push on the other end with a force. The part from the pivot to the load is the load arm. The part from the pivot to the force is the force arm.

Same load, same plank. On the left the pivot is far from the load, so the force arm is short: a lot of force is needed. On the right the pivot is close to the load, so the force arm is long: only a little force is needed. The longer the force arm, the less force we need.

Levers are everywhere! In a bottle opener and in a wheelbarrow, the load is in the middle. In scissors, the pivot is in the middle. It is also why a door handle is far from the hinges: the hinge is the pivot.

Now the pulley. A fixed pulley is fastened in one place and does not move. We pull the rope down and the load goes up. A fixed pulley only changes the direction of the force. The force does not get smaller.

A movable pulley moves up with the load. One end of the rope is tied to the ceiling. Two ropes hold up the load, so the force is halved. But while the load rises 40 centimetres, we have to pull the rope 80 centimetres.

An inclined plane is a ramp. If we push the load up a ramp instead of lifting it straight up, the way is longer but the force is smaller. The longer the ramp, the less force we need.

In a wheel and axle, the handle moves in a bigger circle than the small axle that the rope winds around. Turning the handle needs less force. A screw is an inclined plane wrapped around a rod.

Every simple machine makes the same trade: if the force is smaller, the way is longer. We pay for the force we save with a longer way. So simple machines make a job easier, but they do not save any work.

Summary: in a lever, the longer the force arm, the less force we need. A fixed pulley changes direction, and a movable pulley halves the force. On an inclined plane the way is longer and the force is smaller. None of them saves any work. Now try it in Machines and Energy!