Newton's First Law
An object at rest will remain at rest unless a force acts on it.
An object in motion will remain in motion with the same speed and direction until a force
acts on it.
Ex. A rock will not move until someone pushes it.
A soccer ball will roll in a straight
Newton's Second Law
Force = mass x acceleration. If mass increases, acceleration decreases.
If force increases, acceleration increases.
Ex. If four students push a car instead of only one student, the car will have more acceleration.
An empty bus will have more acceleration
Newton's Third Law
Every action has an equal and opposite reaction (equal in magnitude, opposite in direction)
Ex. As I stand, my feet push on the floor and the floor pushes back on my feet.
If I pull a sled with 3 N (and it does not move), the sled pulls back on me with 3
4) Describe the difference between static and kinetic friction?
Static friction is the friction of something sitting in place, not moving.
Kinetic friction is the friction during motion.
Static friction is higher.
Both "push" in the opposite direction of motion.
What is mass? How is it different than weight in definition and units?
The amount of matter, or atoms, in an object. It is measured in grams or kilograms.
Weight is a measure of force and depends on gravity. It is measured in pounds or Newtons.
Which law explains the relationship between mass, inertia and force?
Newton's 1st Law and Newton's 2nd Law
Define inertia as we have in class.
mass.
How does Newton's 1st Law of Motion apply to hauling logs at a timber factory?
Big logs take a lot of force to overcome inertia and start moving.
Once the logs are moving, it takes a lot of force to stop them.
What does Newton's 2nd Law tell us about the relationship between the mass of an object
and it's acceleration? What about force and acceleration?
As the mass of an object increases, with a constant force, the acceleration will decrease. As the force applied to an object with constant mass increases, the acceleration will
increase.
If we double the mass of an object in motion, what would happen to its acceleration?
Doubling the mass will have the opposite impact on acceleration, making it � of what it was.
If we apply three times the force to an object as the original force applied, what would
happen to the object's acceleration?
Force and acceleration are directly proportional (what happens to one happens to the
other), so if force is X3, acceleration will be X3.
What causes objects to accelerate?
A force that overcomes friction and inertia will cause acceleration.
What two reasons are there for an object not moving when a force is applied?
*It has too much inertia for the force applied.
*It has too much friction for the force applied.
What impact does friction have on the net force (total force) on an object?
Friction "pushes" against motion, so friction will decrease the net force applied to the
object.