Gravity speeds you up as you go down a hill, but what makes you stop. Friction.
Friction is the push or pull that opposes motion between two surfaces that are touching each other
If you are roller blading, you might use the rubber stopper to cause friction against the street to help you stop.
H.W. Pg. 274, ques. 1 & 2. Page 288, 1-10.
Newton’s Three Laws of Motion
Before we talk about the laws, we have to learn about force, which is a push or a pull. Gravity is a force, as well as friction. Everytime you turn a page or open a door, you are using force to do so.
Law #1: Inertia- An object at rest tends to stay at rest, and a moving object moves in a straight line until it is acted upon by an outside force.
In other words, things don’t stop or start by themselves. The reasons things stop is because of friction.
Newton’s Second Law
This law involves force, mass and acceleration.
Law #2: Acceleration depends on the mass of an object and the force pushing or pulling the object.
Force = mass x acceleration, F=mXa
Acceleration = force/mass, a=F/m
It takes less force to accelerate something with a small mass. This is why large trucks need more powerful motors to get them going from a complete stop. If you want to go faster, you have to use more force. Like having to pedal harder on a bike.
Newton’s Third Law
Law #3: For every action there is an equal and opposite reaction.
If you push on a wall, the wall is pushing back at you at the same rate.