📘 What is a Force?
A force is a push or a pull on an object caused by the interaction
with another object.
Forces are measured in Newtons (N).
You cannot see forces, but you can see their effects.
🤲 Contact Forces
These forces act between objects that are touching.
- Tension – a pulling force from a string, rope, or rod
- Friction – resists motion between two touching surfaces
- Air resistance – slows objects moving through air
- Upthrust – pushes objects up in liquids or gases
- Thrust – force from an engine that makes objects move
- Normal reaction force – balances an object on a surface
🧲 Non-Contact Forces
These forces act without objects touching.
- Magnetic force – attraction or repulsion between magnets
- Electrostatic force – force between charged objects
- Gravity – pulls objects with mass towards each other
⚙️ Effects of Forces
- Change speed (speed up or slow down)
- Change direction
- Change shape
Examples:
- Brakes slow a car using friction
- Gravity keeps satellites in orbit
- Squeezing a stress ball changes its shape
📏 Measuring Forces
Forces are measured using a force meter (Newton meter).
Inside the meter is a spring. Heavier objects stretch the spring more,
showing a bigger force.
Before measuring, the meter must be zeroed.
If not, results will have a systematic error.
🔑 Key Words
- Newton (N) – unit of force
- Attractive – pulling objects together
- Repulsive – pushing objects apart
- Systematic error – repeated error by the same amount