10-2: Friction, Gravity, & Elastic Forces
What factors determine the strength of the friction force between two surfaces?
Anticipatory Set
Why can he move an elephant with only his finger?
California StandardsScience Standard 8.2.b: Students know when
an object is subject to two or more forces at once, the result is the cumulative effect of all the forces.
Science Standard 8.2.d: Students know how to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter and friction.
Inputfriction: a force that two surfaces exert on
each other when they rub against each other.static friction: the friction that acts on
objects that are not moving.sliding friction: two solid surfaces slide over
each other.rolling friction: an object rolls across a
surface.
Inputfluid friction: a solid object moves through a
fluid.gravity: a force that pulls objects toward
each other.mass: the measure of the amount of matter
in an objectweight: the gravitational force exerted on a
person or object at the surface of a planet.
Inputfree fall: the only force acting on an object is
gravity.air resistance: an upward force exerted on
falling objects.projectile: an object that is thrown.compression: an elastic force that squeezes
or pushes matter together.tension: an elastic force that stretches or
pulls matter.
Input & ModelingFriction
The strength of the force of friction depends on the types of surfaces involved and on how hard the surfaces push together.There are four types of friction…
Input & ModelingStatic Friction
Input & ModelingSliding Friction
Once the box is moving,
there is sliding friction
between the box and the
floor.
Input & ModelingRolling Friction
Input & ModelingFluid Friction
Input & ModelingGravity
The force of gravity between objects increases with greater mass and decreases with greater distance.
Weight = Mass x Acceleration due to gravity
Input & ModelingGravity
Gravity Between Objects
Input & ModelingGravity and Motion
In free fall, the force of gravity alone causes an object to accelerate in the downward direction.
free fallair resistanceprojectile motion
Input & Modeling
Free Fall
Projectile Motion
Air Resistance
Input & ModelingElastic Forces
Matter is considered elastic if it returns to its original shape after it is squeezed or stretched.
CompressionTension
HOMEWORK CONNECTION Read pages 380-388 in your Science textbook.
Complete the Section 10-2 Review & Reinforce
Write a detailed SUMMARY of the section and complete the UNANSWERED QUESTIONS section of your notes.
Choose two of the remaining Depth & Complexity ICONS in your notes and explain how they relate to this section.