Forces and Newton's First Law
Every time you push, pull, or bump into something, you're applying a force, measured in Newtons (N). When multiple forces act on an object, they combine to create a resultant force - think of it as the 'winning' force after all forces battle it out.
Here's the key bit: if forces are balanced (resultant force = 0), nothing changes. If they're unbalanced, things start moving or change speed. A book sitting on your desk has balanced forces - gravity pulls down whilst the desk pushes up with equal force.
Newton's First Law tells us that objects are lazy - they don't want to change what they're doing. This laziness is called inertia, and it's why you lurch forward when a bus suddenly stops.
Quick Check: A football rolling on grass gradually slows down because friction (an external force) acts against its motion, proving Newton's First Law!
