Download Unit B, Chapter 3, Lesson 4

Unit B, Chapter 3, Lesson 4
What is Newton’s Second Law of
Motion?
Mass, Force, and Acceleration
• It is easier to push or pull an object with
less mass than an object with greater
mass.
– For example: pushing an empty desk needs
less force than a desk filled with textbooks.
• Newton’s second law of motion states an
object’s acceleration depends on the mass of
the object and the size and direction of the force
acting on it.
Mass, Force, and Acceleration
• Force =mass x acceleration
– Force refers to the overall force given to an
object. Mass is to the mass of the objects and
acceleration to the objects change in velocity.
• An object accelerates in the direction of
the force that acts on them.
Mass, Force, and Acceleration
• The greater the force applied, the faster
the object accelerates. When a weaker
force is given, the object will move slower
– For example…when you push a person on
roller skates, they will move faster with a
greater force applied.
• When the acceleration of an object
changes, the amount of force acting on the
object also must be changing.
Falling Objects
• Aristotle, the Greek philosopher, claimed that the
rate at which an object falls depended on its
mass.
– Galileo tested that theory by dropping two cannon
balls at the same time. Aristotle's theory was wrong.
• Two objects dropped with different masses,
should hit the ground at the same time.
• Mass has no control over the rate at which
objects fall. Gravity pulls harder on the object
with more mass, but inertia overpowers gravity.
– The objects have the same amount of acceleration.
Falling Objects
• All falling objects have the same acceleration,
unless air resistance affects them in some way.
– When you drop a flat piece of paper, and a crumbled
up paper, air resistance causes the flat piece of paper
to fall slower.
• Skydivers use streamlining. Streamlining allows
someone or something to increase their
acceleration
– When you streamline an object, you give it the
smallest possible surface area