Newton’s First Law of Motion

Newton’s First Law Objects in motion tend to stay in motion, while objects at rest tend to stay at rest. This is another way of saying INTERTIA

Newton’s First Law of Motion is also called… The “Law of Inertia” Inertia is defined as the property of an object to resist changing its state of motion. (an object tends to keep doing what they were doing until some other force is applied to the object)

How are the 1 st Law & 2 nd Law related? The 2 nd Law of Motion Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Everyone knows that heavier objects require more force to move the same distance as lighter objects.

the Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation: or FORCE = MASS times ACCELERATION

An object with a lot of inertia takes a lot of force to start or stop. A big truck would have more inertia than a small car. A small would have more inertia than a bike. A bike would have more inertia than a pair of roller blades Inertia is directly dependant upon the mass of the object in question.

F = ma Demo: Add a force to the chair to make it accelerate. Add a force to the chair with more mass to make it accelerate. It takes more force to get a larger mass under acceleration It’s a lot easier for you to push a friend on a bike instead of having to push their car when they run out of gas

This is an example of how Newton's Second Law works: Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car. F= 1,000 x 0.05 Answer = 50 N

What do you think would happen if you kept the mass constant and increased the force? You would increase the acceleration.

This is why Top fuel Dragsters, Funny Cars, all racing cars want to keep the weight down in order to increase acceleration On the other hand, Tractor Pullers want to have more weight in order to give an advantage by getting the tires to get better bite.

So if it takes more force to get a object with more mass to start moving or accelerate then…What happens when it wants to stop? It takes the average train over a mile to stop! The 1 st and 2 nd law demonstrates why train wrecks can be so disastrous.

And it takes an Ocean Liner a couple of miles to stop…