1. Chapter 4
Laws of Motion

2. Forces What is a force? Push or a pull Contact or field
Forces are vectors…
Magnitude and direction
Units
Newtons, N, kg∙m/s2

3. Newton’s Laws Newton’s First Law Inertia
mass
A net, unbalanced force is needed to change an object’s velocity

4. Newton’s Laws Newton’s Second Law Acceleration
Proportional to the amount of net, unbalanced force on the object
Inversely proportional to the mass of the object
netF = ma

5. Newton’s Laws Newton’s Second Law Acceleration
Proportional to the amount of net, unbalanced force on the object
Inversely proportional to the mass of the object
netF = ma

6. Newton’s Laws Newton’s Third Law Action-reaction
Forces in nature always exist as pairs
An action force produces a reactive force that is equal in magnitude, but opposite in direction
F = -F΄

7. Newton’s Laws

8. Gravitational Force

9. Gravitational Force Newtonian and Einsteinian theories
Newton: mutual attraction of objects with mass
Einstein: objects with mass distort the space around them
Proportional to mass
Inversely proportional to the distance (centers of mass) squared

10. Gravitational Force

11. Gravitational Force Weight Gravitational force action on an object
W = mg
gEarth = -9.8 m/s2

13. Free body diagrams https://www.youtube.com/watch?v=gDk2te4nrIo

14. Friction Friction is… Is friction a good thing or a bad thing?
A force that opposes motion
Static
kinetic
Is friction a good thing or a bad thing?

15. Force of Friction Calculation
There are two factors that influence the amount of friction
Normal force
Coefficient of friction (interaction between surfaces)
The coefficient of friction is dimensionless, has no units

16. Force of Friction Calculation
Force of friction = (coefficient of friction) x (normal force)
f = µ Fn

17. Force Applied at an Angle

18. Inclined Planes

19. Inclined Planes

20. Inclined Planes
The force of weight needs to be resolved into x and y axis components that run parallel and perpendicular to the surface of the plane

21. Inclined Planes