1. Forces & Newton’s First Law
Dynamics I
Forces & Newton’s First Law

2. 4 Natural Forces
Gravity: acts between all masses in the universe and has “infinite” range

3. Electromagnetic (EM) Force: acts between electrically charged particles and “magnetically charged” poles

4. Strong Nuclear Force (aka Strong Force): Binds nucleons together (very short ranged but extremely strong)

5. Weak Nuclear Force (aka Weak Force): Acts between particles (e. g
Weak Nuclear Force (aka Weak Force): Acts between particles (e.g. Fermions) and is responsible for radioactive decay.

6. What is a force? A force is a push or a pull on an object
An object’s motion will change with time if the forces acting on it are unbalanced
Change in motion  change in velocity
Change in velocity  acceleration
If the forces are balanced the object’s motion will not change
No change in motion  velocity is constant
Velocity is constant  acceleration is zero

7. Field Forces vs. Contact Forces
Contact forces happen when objects touch
Field forces act at a distance
Gravity
Electrostatic forces
Magnetic forces

8. Force is a VECTOR!
To find out if the forces on an object are balance or unbalanced, we must add them as vectors

9. Newton’s First Law of Motion
An object at rest remains at rest, and an object in motion continues in motion with constant velocity unless the object experiences a net external force
“At rest” means zero velocity
“Net force” means the forces are unbalanced and do not add up to zero

10. Inertia
The tendency of an object with mass to resist a change in motion is called inertia
Newton’s first law is called the law of inertia: it says that without a net force an object’s motion will remain unchanged
Mass gives objects the property of inertia
The greater the mass, the greater the inertia