Conceptual Physics Newton's First Laws

1. Dynamics
 how things move

2.  The tendency of a mass to resist motion.
 Imagine an empty box: This is easy to push
 Imagine a box full of books: This is hard to push
Which has the greater inertia?

3. Newton (16-1700 AD)
Mass is a measure of inertia
The more mass you have, the less it wants
to change its state of motion.
1st Law (Law of Inertia)
An object in motion tends to stay in
motion with a constant velocity and an
object at rest tends to stay at rest, unless
acted on by an unbalanced force.

4. Force
 a push or pull on an object
(measured in Newtons unit: N)
Net Force (Fnet)
 is the sum of all the forces acting on
an object
Balanced Unbalanced
F1 = 2 N F2 = -2 N F1 = 2 N F2 = -5 N
Fnet = 2 + -2 = 0 N Fnet = 2 + -5 = -3 N

5.  Force has both magnitude (how much) and direction.
North or Up is +y
South or down is –y
East or right is +x
West or left is -x
 1200 N – 800 N = 400 N North or Up
 600 N – 800 N = -200 N South or down
 In the third example, the only force
remaining is the 20 N force West

6. 1. Contact 2. Noncontact
a. Any push or pull No touch
that requires touch required

7.  Tension: Caused because of rope, wire, etc.
 Normal: perpendicular to ground pushing up
on object.
 Friction: opposes Also: Any push or pull
motion
Forces: Noncontact
Weight: Due to gravity, mass and distance from
earth mass x gravity or mg

8. F
1. Draw the object as a blank rectangle:
2. Draw the force vectors as coming out of the
box. Label each of the vectors with the
name of the force.
3. Check to make sure that all forces are
accounted for.

9.  An object is pushed to the right. Friction opposes
the motion.
Normal or FN
Friction or Ff
Push Force or FP
Mass x gravity or mg force

10.  An object hangs from the ceiling
Notice there
is no normal because
there is no Tension or T
contact with a surface.
Mass times
gravity or mg

11. Object on an inclined plane at rest.
Normal is to incline. No
rm
Fri al
c tio
n
mass x gravity