Transcript Chapter 10 Section 2

Chapter 10 Section 2
Friction, Gravity, and Elastic
Forces
Friction
• Friction is a force that two surfaces exert
on each other when they rub against each
other.
• Friction is caused when the irregularities of
one surface come into contact with those
of another surface,
• The strength of the force of friction
depends on the types of surfaces involved
and how hard the surface push together.
Types of Friction
• 1. Static Friction: Is a friction that acts on
objects that are not moving.
• 2. Sliding Friction: Occurs when two
solid surfaces slide over each other.
• 3. Rolling Friction: Occurs When an
object rolls over a surface.
• 4. Fluid Friction: Occurs when a solid
object moves through a fluid. (fluids in science are all
the liquids and gases)
Gravity
• Gravity is a force that pulls objects toward
each other.
• Newton was the first scientist that talked
about Gravity
• Law of Universal Gravitation states that
the force of gravity acts between all
objects in the universe.
• Gravity depends on Mass and Distance;
The force of gravity between objects
increases with greater mass and
decreases with greater distance.
• The measure of amount of matter in an
object is its mass. The SI unit of mass is
gram (g) or kilogram (Kg).
• Weight is a measure of gravitational pull.
• Weight=Mass X Acceleration due to gravity
• Acceleration due to gravity is 9.8m/s/s
• Newton is unit for Weight. (N)
Gravity and Motion
• Free fall: An object is in free fall when the
only force acting on the object is gravity.
• In Free Fall, the force of gravity alone
causes an object to accelerate in the
downward direction.
• The acceleration due to gravity is
9.8m/s/s.
• Air Resistance is an upward force exerted
on falling objects.
• Air Resistance is a type of fluid friction
acting on all falling objects.
• Objects with greater surface area
experience more air resistance as they
fall.
• When objects are thrown horizontally they
travel in a projectile motion.
• Matter is considered Elastic if it returns to
its original shape after it is squeezed or
stretched.
– Compression is an elastic force that
squeezes or pushes matter together.
– Tension is an elastic force that stretches or
pulls matter.