1. Forces & Motion

2. What is a Force? Force: push or pull Unit: Newton (N)
Kg x m/s2
Vector: has both magnitude & direction

3. Combining Forces Use vector addition
Net Force: the total force acting on an object
Balanced Forces: when the net force is zero
No motion occurs
Unbalanced Forces: when the net force is not zero
Motion occurs (acceleration or change in direction)

4. Balanced Forces:

5. Unbalanced Forces:

6. Friction Friction: a force that opposes (acts opposite to) motion
Four types:
Static
Sliding
Rolling
Fluid

7. Types of Friction
Static: friction force on objects that are not moving (greatest friction force)
Sliding: friction force on an object as it slides over another
Rolling: friction force on an object as it rolls over another (ex. Ball bearings)
Fluid: friction force on an object in a fluid (liquid or gas) (ex. Air resistance)

8. Gravity
Gravity: downward force pulling objects toward the center of Earth
Acceleration on Earth due to gravity = 9.8 m/s2
Terminal velocity: constant velocity that a falling object reaches when the force of gravity is equal to the air resistance

9. Projectile Motion
An object thrown forward will follow a curved path due to gravity
The combination of an initial forward velocity and the downward vertical force of gravity causes the object to follow a curved path

10. Projectile Motion

11. Scientists who contributed to the ideas about Force & Motion
Aristotle: incorrectly proposed that force is required to keep an object moving at a constant speed
Galileo: studied constant acceleration due to gravity
Newton: defined force & mass; introduced laws of motion

12. Newton’s First Law of Motion
Law of Inertia
An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an outside force
If the net force = 0, then the object’s state motion will remain unchanged

13. Newton’s Second Law of Motion
The force acting on an object is equal to the mass of the object times the object’s acceleration
Force = mass x acceleration (or F = m x a)
Units: N = kg x m/s2

14. Weight & Mass Weight: the force of gravity acting on an object
W = m x g
same equation as F = m x a
Changes depending on the gravitational force
Mass: a measure of inertia on an object (how much matter is within an object)
Constant no matter what the gravity

15. Newton’s Third Law of Motion
For every action there is an equal and opposite reaction
Forces occur in pairs
Not all forces create motion

16. Momentum The product of an objects mass times its velocity
An object with large momentum is hard to stop
Momentum = mass x velocity
M = m x v
Units kg*m/s = kg x m/s

17. Momentum

18. Law of Conservation of Momentum
In a closed system, the loss of momentum of one object equals the gain in momentum of another object
Momentum is conserved

19. Universal Forces
Electromagnetic Forces: forces associated with charged particles (electric & magnetic)
Nuclear Forces: forces that occur within the nucleus of an atom
Gravitational Forces: an attractive force between any two masses

20. Newton’s Law of Universal Gravitation
Every object in the universe attracts every other object
Closer distance = greater force
Larger mass = greater force