Transcript Force Diagrams

Force Diagrams (Free-body Diagrams)
A force diagram is simply a
diagram showing all the
forces acting on an object,
the force's direction and
its magnitude
It is a simplification of the
picture that shows just the
forces.
Steps for drawing a force diagram:
1. Identify the object you will draw a diagram for.
2. Identify all the forces acting directly on the object
and the object exerting them
3. Draw a dot to represent the object of interest.
4. Draw a vector to represent each force. Draw it in the
direction the force is being exerted, and label it by (a) the type
of force, (b) the object exerting the force, and (c) the object
receiving the force (which will be you object of interest).
5. If the object is stationary or is moving at a constant
velocity, the vectors should graphically add up to zero. If
the object is accelerating, the sum of the vectors should
produce a vector in the same direction as the acceleration.
Types of forces typically used
Force
Symbol
Magnitude
1.Gravity
(weight)
F(G)
= mobject*g
2.Normal
(surface)
F(N)
any (up to breaking load)
perpendicular to
surface
3.Tension
F(T)
any (up to breaking load)
along
string/rope/chain
F(fr)
not slipping: between zero
and ms*F(N)
slipping: = mk*F(N)
Direction opposing
motion.
4.Friction
Direction
(9.8 m/s2)
Downward
Writing down the sum of the forces
1. Identify direction of every force and of acceleration.
2. Pick a coordinate system to minimize the number of things
(forces and acceleration) that must be broken into components,
especially unknown values
3. Draw the components for any forces or acceleration that does
not lie along the X or Y axis, and identify the angle that is given (or
being looked for).
4. Pick one direction and write down all the forces or components
of forces in that direction, using positive and negative signs to
identify those in the positive and negative directions.
5. Set the sum of the forces in that direction as equal to the mass
multiplied by the acceleration in that direction. (If not moving or
moving at a constant velocity in that direction, acceleration will be
zero.)
6. Repeat for the other direction.
Websites
a. Free-body diagrams
b. Newton’s Laws
c. More Of Newton
d. More free Body diagrams