Transcript Chapter 12 Lesson 1

Chapter 12
Lesson 1
“Forces”
I. Force
A. Def – A push or a pull on an object.
1. Can cause movement
B. Measured in Newtons (N)
1. Units (1 kg x 1 m/s2)
C. Arrows
1. Used to show forces
2. Which arrow shows the largest force?
#1
#2
D. Combining Forces
1. Net force – combination of all forces
on an object
E. Balanced Forces
1. When the net force equals zero
2. Ex. Tug of War (equal)
F. Unbalanced Forces
1. When forces do not equal each other
2. Ex. Tug of War (not equal)
3. When an unbalanced force acts on
an object, the object accelerates.

Forces acting in opposite directions can
combine to produce an unbalanced force.
15 N
Net force is equal to 7 N to left.
8N
G. Friction (pg. 359-360)
1. Def – A force that opposes movement
a. Always produces heat
2. 4 Types
a. Static friction (non-moving) –
always acts in direction opposite the force
b. Sliding friction – less than static
friction so less energy required to keep an
object moving than to start it.
c. Rolling friction
-100 to 1000x’s less than
sliding or static friction
d. Fluid friction – feel it when stirring
a cake batter. The faster you stir,
the greater the friction.
-fluid or gas
- air resistance – we will see
this become a big issue during
the bobsled events of the
Winter Olympics.
H. Gravity
1. Force that acts between any two objects
2. On Earth…
-gravity pulls us down towards the
center
3. Gravity pulls at 9.8 m/s2 (everything)
4. Terminal velocity
a. Gravity = Air resistance
5. Falling Objects
A. Bowling Ball vs. Marbles
1. Both hit the ground at the same time.
B. Air Resistance
1. Def – the force air exerts on a moving object
2. Feather vs. Brick
3. Crumpled Paper Test
II. Projectile Motion
A. Def – anything thrown or shot through the
air.
#1 Fact – projectiles follow a curved path
#2 Fact – projectiles are affected by both
horizontal and vertical motion. (pg. 362)
12.1 wks
1.
2.
3.
4.
Give an example of a balanced force.
Unbalanced force.
What are the 4 types of friction? Give an
example for each.
What is the rate of acceleration objects fall
towards the earth at? What is terminal
velocity?
If two identical balls are knocked off of a
table at the same time, which will hit the
floor first? Why?