forces and motion

What is a force?
a push or a pull
ex. throw a ball or pick up a bat
What are different types of forces?
gravity, magnetism, friction, the force from a human or an object
What is friction?
a force that occurs when 2 surfaces rub against each(hands rubbing)
What are the 4 types of friction?
static-between stationary objects-keeps a book on a desk
sliding-one object slides over another (can cause heat)
a box being pushed across a carpet
rolling-when two objects roll across one another - ballpoint pen on paper, a car on a driveway
fluid friction- when an object moves through a liquid or air (air resistance)
-a fish gliding through water
-a parachute being pulled up by air resistance
What is motion?
when an object changes position ex. swinging a bat, hitting a ball
What is speed?
how quickly something travels-
distance over time 35 miles per hour
What is volocity?
speed with direction
25 miles per hour
What is gravity?
a force that pulls all objects toward one another-
gravity from the sun and planets and keeps the planets in alignment and orbiting the sun
What is weight?
the measure of gravity's force.
measured in newtons
What is mass?
the amount of matter or material in an object.
-measured in kg
What is Newton's first law of motion?
an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an outside force(friction)
What is an inertia?
it is natural for objects to resist any changes in their state of motion. it does not want to stop.
this resistance to stopping the motion is called inertia.
inertia depends on mass. the more mass an object has the more powerful the inertia (the resistance to changing or stopping the motion)
Ex. a boulder that is pushed down a hill. it will pick up speed and keep rolling until a powerful force stops stops it.
Example of Newton's first law
when a toy car is resting on the floor in one spot it does not move. in order to get it to move you must use a force (a push). when it starts to move it will continue to move unless a force (friction) stops it from moving. the friction is from the wheels rubbing against the floor and even the air it moves through creates friction.
What is Newton's second law of motion?

Force=mass times acceleration
how fast the objects moves (acceleration) depends on the force that puts the object in motion and how much mass the object has.
it takes more force to acceleration or speed up a more massive object.
Ex. a light object would not need that much force to speed up its motion.
Ex. a heavy object would need a strong force to speed up its motion.
What is Newton's third law?
for each action there is an equal and opposite reaction.
Ex. students on roller skates pass a basketball to each other. for every push forward of the basket ball the student will roll backwards.
Ex. gravity is pulling us towards the earth, but we are pulling the earth towards us. so we are in constant battle.