2/16/2012
Post date: Feb 16, 2012 6:5:25 PM
Chapter 12 Review
Forces
A push or a pull
An interaction that causes acceleration
Measured in Newtons (N)
Balanced forces do not cause a change in motion, unbalanced forces do
Friction - the force that opposes motion (makes it harder for objects to move, eventually slows them down and stops them)
Gravity
Acts downward, toward the center of the Earth
Falling objects experience gravity downward and air resistance upward (which slows the fall)
Falling objects eventually have air resistance and gravity balance out, meaning the object stops accelerating (this is called terminal velocity)
Newton's 1st law
An object's state of motion will not change unless it is acted on by an unbalanced force
Newton's 2nd law
Acceleration of an object depends on the force applied to it and the mass of the object
Acceleration = Force / mass
Weight and Mass
weight = mass x acceleration of gravity
acceleration of gravity on Earth = 9.8 m/s2
acceleration of gravity on moon = 1.6 m/s2
Weight depends on the amount of gravity, but weight does not.
Newton's 3rd law
Whenever an object exerts a force on a second object, the second object exerts and equal and opposite force on the first object
Universal forces
Electromagnetic force - occurs between charged particles - opposites attract, likes repel
Strong nuclear force - occurs over short distances (between protons and neutrons in a nucleus)
Weak nuclear force - occurs over short distances (between protons and neutrons in a nucleus)
Gravitational force
attractive force between all pairs of objects
Strength of force depends on the sizes (masses) of the two objects and the distance between them.
Review worksheet or page 385-386: pick 15 problems
Chapter 12 Test tomorrow