Forces and Motion

Screwdrivers are used for many things - be careful!

Physics Narrative for 11-14 Supporting Physics Teaching

Screws or tins?

Explaining how screwdrivers work can be tricky because they are designed for one thing but often used for other jobs (especially flat-bladed screwdrivers). For example, the screwdriver might be used at one moment to tighten a screw in a kitchen cabinet and at the next to lever the lid off a tin of treacle. Driving in screws is made easier if the handle is made larger in diameter than the screw head. In this way the small force exerted by the hand on the handle becomes a large pair of forces acting on the slot in the screw head. This increase in force is traded for a decrease in the distance moved by the screw head compared to the hand. The screwdriver, used like this, is a force-multiplier.

If you doubt this try exerting a force on the screw with your hand, directly. If you still find the screw rather hard to drive in, choose a screwdriver with a thicker handle!

However, if you are using the screwdriver to lift up a lid and are still having difficulty, then choose a screwdriver with a longer shaft. You will find longer and shorter screwdrivers in toolkits – not for opening cans – but longer screwdrivers simply offer easier access to awkwardly placed screws (maybe deep inside a computer cabinet).

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