Touching, or not
A comb rubbed on dry hair lifts paper bits. It does not touch them.
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The rule
A contact force needs touching. A non-contact force acts across a gap. A gap is the empty space between two objects.
Muscular force comes from muscles. Friction acts between two rubbing surfaces. Electrostatic force comes from a charged object, like a rubbed comb. Gravitational force, or gravity, is the Earth's pull on things.
| Force | Touching? | Example |
|---|---|---|
| Muscular | Yes | Pulling a stump from soft ground |
| Friction | Yes | A brake pad rubbing a rim |
| Magnetic | No | A fridge magnet holding a note |
| Electrostatic | No | A rubbed comb lifting paper bits |
| Gravitational | No | A coconut falling from a palm |
Gravity only pulls. Magnetic and electrostatic forces can pull or push.