Forces
Contact and non-contact forces, friction, gravity
Forces
A force is a push or pull that can change an object's speed, direction, or shape. Contact forces require physical touch (friction, applied force). Non-contact forces act at a distance (gravity, magnetic force). Force is measured in newtons (N).
Example
Forces in Action
Gravity pulls a ball downward. Friction slows a car when brakes are applied. A magnet attracts iron nails without touching them. Balanced forces mean no change in motion; unbalanced forces cause acceleration.
Note
Key Point
Friction can be helpful (shoes gripping the ground) or unhelpful (wearing down machine parts). Gravity keeps us on Earth and holds the moon in orbit.
Key Vocabulary
ForceA push or pull that can change an object's motion or shape, measured in newtons
FrictionA force that opposes motion between surfaces in contact
GravityThe force that pulls objects towards the centre of the Earth
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