Four Fundamental

Forces

 

aForce- the cause of an acceleration or the change in an objects motion.

 

THE FOUR FORCES

 

·      Force Weight

·      Force Normal

·      Force Applied

·      Force Friction

 

Definitions of individual forces:

 

1.     Force Weight (FW) - an objects mass times gravity

2.     Force Normal (FN)- Fwcosθ

3.     Force Applied (FA)- Fwsinθ

4.     Force Friction (Ff)- FN times coefficient of friction  

 

Other Information needed:

 

1.     Coefficient of Friction (U)- a number between 0 and 1 that tells you how slick or “sticky” a surface is

2.     Net Force (NF)- FA – Ff

3.     Force= Mass times Acceleration- F = MA

4.     The Unit of force is Newtons

5.     Gravity is 9.8 m/s

 

 

 

EXAMPLE PROBLEM

 

A 28Kg box is put on a 24 degree incline plane.  The ramp is 4 meters long.  The coefficient of friction of the ramp is 0.18.

A)   Solve for acceleration.

 

 

 

28kg

 

24

FW= 28 x 9.8 = 274.4N

FN= 274.4 cos (24) = 250.68N

FA= 274.4 sin(24) = 111.61N

Ff = 250.68 x 0.18 = 45.12N

 

Force Net = 111.61 – 45.12 = 66.49N

 

** USE  F = MA TO GET ACCELERATION! F= FORCE NET!

 

66.49= 28 x (A)

 

Ö A= 2.37 m/s^2

 

    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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