Unit 1 - FORCES Handout
Forces - any straight-line ______________ or ______________
A.
Representing
Forces
1. Unit of force
a) lb. (English)
b)
______________
(metric) (weight of one ___________) ****
2.
Forces are vectors - described using ___________ & ___________
Solving problems with vectors require a special branch of mathematics
Review - Scalar ( ______________ only) ex) ______________
3. When solving problems and drawing pictures, forces are represented as
_______________
***Length shows ____________***arrow shows _____________
B. Combining Force Vectors
Resultant ________________________________
1) Methods for finding resultant.
(a) Case 1 - ___________________
(Angle between forces = ______________)
Answer:
RULE when Ð = 0 _________________________
|
(b) Case II - Forces acting in _______________
Resultant = _________________
RULE If Ð = 180° - __________ _________________________________________________ |
(c) Case III Forces acting at an angle
C. Combining Forces - Range of possible resultants
Example) Forces of 100N and 30N force act on a body.
¨
Largest possible resultant = ______________
¨ Smallest possible resultant = ______________
ü ______________ Forces - Smallest Possible Resultant
ü ______________ Forces - Largest Possible Resultant
Example - Which pair of concurrent forces may have a resultant of 20nt?
¨
Big Hint: Find the range of possible resultants
for each choice (nt =
a) 5 nt + 10 nt
b) 20 nt + 20 nt
c) 20 nt + 50 nt
d) 30 nt + 5 nt
Answer _______________
D. Finding resultants when angle between forces = 90°
Ex 1) A 5N force pulls an object north while a 12 N force is pulling the object West. Find the resultant
Scale 1N = 1cm
Two Methods
Method One - Graphical
Method -(Draw It!!)
1. _______________________________________________
2. _______________________________________________
3. _______________________________________________
4. _______________________________________________
Method Two - Use trig. and Pythagorean (More accurate and easier)
1. Use a2 + b2 = c 2 (To find magnitude) _______________
2. Tanq = Opp./Adj = q = _________
E. Equilibrant - the balancing force of 2 or more vectors
The Equilibrant is always_______________________________________
___________________________________________________________________________
ü If… Resultant = 5 N 53° N of W
ü Then… Equilibrant = __________________
Example 2) Concurrent forces (acting together) of 10 nt east and 10 nt south act on an object.
Find the resultant and the equilibrant.
1. ____________________
2.
__________________
Answer: Resultant = __________________ Equilibrant = ____________