11.2 Types of Forces
Question of the Day:
If I push a beaker to slide it across the counter, why
does it stop?
Sort the following forces as Contact Force or Field Force
Air Resistance
Applied
Electrical
Frictional
Gravitational
Magnetic
Normal
Spring
Tension
Sort the list on a whiteboard as a team.
Contact Force - Applied Force
A force that is applied to an object by a person or another object.
Contact Force - Normal Force
The normal force is the support force
exerted upon an object that is in
contact with another stable object.
What is providing a normal force for
Spongebob?
Friction
The force exerted by a surface as an object moves across it or
makes an effort to move across it.
Friction results from the two surfaces being pressed together
closely, causing intermolecular attractive forces between molecules
of different surfaces. (Depends on what the materials are made
from to determine how much friction there will be.)
Though it is not always the case, the friction force often opposes
the motion of an object.
Friction
Sometimes we ignore friction to make the
math easier.
Contact Force - Air Resistance
The air resistance is a special type of
frictional force that acts upon objects
as they travel through the air.
We can ignore air resistance for small
objects moving at low speeds.
Tension
The tension force is the force that
is transmitted through a string,
rope, cable or wire when it is
pulled tight by forces acting from
opposite ends.
Springs
The spring force is the force exerted by a compressed or stretched spring
upon any object that is attached to it.
Types of Forces Examples
Go to Google Classroom.
Click on the link to the Jamboard.
Provide one example of each type of contact force.
What objects or scenarios would you see each type of force?
Gravitational
The force of gravity is the force with which the earth, moon, or other massively
large object attracts another object towards itself.
Fgrav = m * g
where g = 9.8 N/kg (on Earth)
and m = mass (in kg)
What keeps the balloon stuck to the wall?
Draw on the whiteboard what you think is happening.
Electrical
Attraction between
opposite charges
or repulsion between like
charges.
https://phet.colorado.edu/sims/html/balloons-and-static-electricity/latest/balloons-and-static-electricity_en.html
Magnetic
Attraction or repulsion that arises
between electrically charged particles
because of their motion or the alignment
of atoms in a substance.
https://www.youtube.com/watch?v=
Vt8NOdINJ1s
Free Body Diagrams
A book is at rest on a tabletop. Diagram the forces acting on the book.
Free Body Diagrams
A car is coasting to the right and slowing down. Ignore air resistance.
Diagram the forces acting upon the car.
Net Force