1. Mass vs. Weight

2. Newton’s First Law of Motion
INERTIA is the tendency of an object to resist changes in their state of motion.
Mass is a measure of inertia.
Object with small mass -----> has less inertia
Object with large mass > has more inertia
Ex: Imagine how difficult playing softball with a bowling ball.
Hard to pitch
Hard to change its direction

3. What is mass?

4. Mass is the measure of the inertia of an object
The more mass an object has, the harder it is to move it (or stop it)
Mass ≠ Weight
Weight changes due to gravity
You can be “weight-less” in space...but you’re not mass-less!
Mass

5. Newton’s First Law of Motion
MASS is a measure of the amount of matter in an object
Mass will not change as you move from place to place
WEIGHT is a measure of the gravitational force exerted on an object
(the force with which Earth’s gravity pulls on a quantity of matter)
The force varies from place to place
Ex: Weight of an object will be different on Earth than on the moon

6. Mass, Continued Mass is a PROPERTY Weight is a FORCE
Measured in kilograms (kg)
Weight is a FORCE
Measured in newtons (N)
A force, in simple terms, is either a push or a pull

7. (Pushing a Car) Would pushing a car be any easier on the moon?
No!
The car has the same mass, even if the weight is lighter

8. Review Newton’s First Law of Motion

9. Review

10. Net Force: Force: An action exerted on an object (a push or a pull)
in order to change the state of rest or motion
of an object.
Measured in Newtons (N)
Net Force:
Combination of all the forces acting on an object. (add them up)

11. Two teams that are evenly matched play tug-o-war NOTHING HAPPENS
Balanced Forces
If all of the pushes and pulls are even on an object, then the object “keeps on doing what it was doing”
Tug-o-war
Two teams that are evenly matched play tug-o-war
NOTHING HAPPENS

12. Balanced Forces when net force is zero Does not cause a change
in object’s motion

13. Unbalanced forces cause objects to change velocities
Tug-o-war
Two teams that are unevenly matched play tug-o-war
One team will win

14. Unbalanced Force
What happens when an object has an unbalanced force acted upon it?
Unbalance forces cause acceleration!!

15. If the forces are… Equal – Unequal – Nothing happens
Ex: A book sitting on a shelf
Fg = 25 N
FN = 25 N
Unequal –
The object changes what it is doing
Ex:
FA = 25 N right
FA = 100 N left

16. F = mass x acceleration F = m a Newton’s 2nd Law
The acceleration of an object is directly proportional to the net force acting on the object and is inversely proportional to the mass of the object. In other words:
F = mass x acceleration
F = m a

17. F = m*a m Fg g m
“Weight” g