Lesson 2 of 7
Contact and non-contact forces
Goal: Tell contact forces from non-contact forces.
A contact force acts only when two things touch. A non-contact force acts across a gap.
Contact forcesFriction, air resistance, water resistance, upthrust and tension
Non-contact forcesGravity, magnetic force and electrostatic force
- Gravity is a pull between any two objects. The Earth is so massive that its pull is the one you notice.
- Weight is the pull of gravity on an object. It is a force, so it is measured in newtons.
- Upthrust is the upward push of water or air on an object. It is what makes a boat float.
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Key words in this lesson
Force A push or a pull
Newton The unit of force
Contact force Acts only when objects touch
Non-contact force Acts without the objects touching
Friction Opposes sliding between two surfaces
Air resistance Drag from moving through air
Water resistance Drag from moving through water
Upthrust Upward push from a liquid or a gas
Weight The pull of gravity on an object
Tension The pulling force in a rope or string