1. Section 1: The Nature of Force
Force – a push or pull on an object; causes an object to accelerate.
3 m/s
0 m/s

2. F = ma Calculating Force Force = (mass)(acceleration)
measured in units of:
kilogram-meter/second squared
(kgm/s2)

3. kilogram-meter/second squared
a.k.a.
Newton
(N)

4. Two Types of Forces
balanced forces – forces of equal strength & acting in opposite directions; net force always equals zero Newtons.
5 N
5 N
Net force = 0 N

5. unbalanced forces – forces of unequal strength &/or act in different directions; causes an object to move.
2 N
5 N
Net force =
3 N
3 N

6. Unbalanced Forces
5 N
8 N
3 N
~7 N
5 N
5 N

7. Section 2: Friction & Gravity
friction- the force that two surfaces exert on each other when they rub against each other.
4 Types of Friction: (strongest to weakest)
Static
Sliding
Rolling
Fluid
- air resistance is the most common form.

8. gravity – a force that pulls objects toward each other.
Gravity causes objects to accelerate toward earth at:
9.8 m/s2.

9. Gravity also causes:

10. Law of Universal Gravitation
states that due to gravity every object in the universe is attracted to every other object in the universe.

11. w = mg Weight weight is the gravitational pull on an object.
weight = (mass)(gravity)
w = mg
measured in units of:
Kgm/s2 a.k.a. Newtons

12. Calculate your REAL weight Step 1) Find your mass:
# of lbs / 2.2 = # of kgs.
Step 2) Calculate your weight
w = (# of kgs.)(9.8 m/s2)

13. Gravity in the Solar System
Moon
1.2 m/s2
Venus
7.98 m/s2
Jupiter
31,000 m/s2
Sun
3,244,816.1 m/s2

14. Newton’s First Law (Law of Inertia)
An object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity, unless an unbalanced force acts upon it.

15. inertia – the tendency of an object to resist changes in its motion.

16. F = ma Newton’s Second Law
force, mass and acceleration are related with the formula:
F = ma

17. 50 N
6 m/s2
300 kg

18. 12 m/s2
100 N
300 kg

19. 6 m/s2
100 N
600 kg

20. Newton’s Third Law
if one object exerts a force on another object, then the second object will exert a force of equal strength in the opposite direction back on the first object.
Fuel
Gas

22. momentum – the product of an object’s mass and velocity.
momentum = (mass)(velocity)
p = mv
measured in units of:
kilogram-meter/second

23. Law of Conservation of Momentum
states that: the total momentum of a group of objects remains constant
in other words:
the total momentum of objects before a collision equals the total momentum after a collision.

24. Before the collision 0.3 kg 0.25 kg C 1.5 m/s 0 m/s p = 0 kgm/s8 C
1.5 m/s
0 m/s
p = (0.25 kg)(1.5 m/s)
p = (0.3 kg)(0 m/s)
p = 0 kgm/s
p = .38 kgm/s
pt = .38 kgm/s + 0 kgm/s
pt = 0.38 kgm/s

25. After the collision 0.3 kg 0.25 kg C 0.75 m/s 0.63 m/s p = 0.19 kgm/s8
0.75 m/s
0.63 m/s
p = (0.25 kg)(0.75 m/s)
p = (0.3 kg)(0.63 m/s)
p = 0.19 kgm/s
p = 0.19 kgm/s
pt = 0.19 kgm/s kgm/s
pt = 0.38 kgm/s