Transcript Forces and the Laws of Motion

Basic Info: balanced Forces

Objects are balanced only if their net force is zero in
both the vertical and horizontal directions


Meaning all the forces in the x direction add up to zero AND
all the forces in the y direction add up to zero
All forces that act in a angle needs to be broken into
components using trig.

Meaning using a right triangle with x and y components.
Vector Components

In order to find the
components of a
vector (like force) you
will need to use those
timeless Trigonometric
Functions.
Vector Components


So we have a person
pulling a sled 30o with
respect to the
horizontal at a force of
50 N.
We need to think of it
like the sled being
pulled vertically and
horizontally at the same
time, giving it both
components.
Fy
Θ=30o
Fx
Vector Components



In order to calculate the
components, we need to
shift Fy to make a right
triangle.
Then we can use trig
functions to solve for Fy
and Fx like they are sides of
a right triangle.
To solve for Fx, we will use
cosine because it is adjacent
and we have the
hypotenuse.
Fy
Θ=30o
Fx
Vector Components

To solve for vx, we will use cosine
because it is the adjacent side and we
have the hypotenuse.
adj
cos  
hyp
F
cos   x
F
Fx  F cos 

To solve for vy, use the same process but
with sine.
sin θ 
sin θ 
opp
hyp
Fy
F
Fy  F sin θ
Fy
Θ=30o
Fx
Fy equals?
A.
B.
C.
D.
43.3 N
25 N
28.9 N
50 N
Fy
Θ=30o
sin θ 
sin θ 
opp
hyp
Fy
F
Fy  F sin θ
adj
hyp
F
cos   x
F
Fx  F cos 
cos  
FBD Example 1

A 50 kg mass is
suspended from two
wires, as in the
diagram below. What
is the tension in the
wires?
FBD Example 2
A 25.0 N picture is hanging from two wires.
The wires make a 30˚ angle with the top of
the picture. Calculate the tensional force on
each wire.