Download Newton`s Toy Box- Notes Activity #1: Intro to Motion (supporting info

Newton’s Toy Box- Notes
Activity #1: Intro to Motion (supporting info on pp. 2-4, 10-11, 22 in the reader)
A force is a push or pull. Examples of a force are gravity, magnetism, friction,
etc.
Velocity is speed in a particular direction. Altering the moving object’s speed
and/or direction can change velocity.
An unbalanced external force changed the direction of the path of the
sphere in activity #1. It was unbalanced because it was applied to only one
side of the sphere. It was external because the force was applied to the
surface of the sphere. This type of force is also called a net force.
Newton’s First Law of Motion states that an object will remain at rest or in
uniform motion unless acted on by an unbalanced external force.
An object’s tendency to remain at rest or in motion is inertia. Newton’s first
law of motion is also called the inertia principle.
Activity #2: Gravity and Balance
(pp. 4-5, 8)
Gravity is the force pulling objects toward the center of the Earth. The
gravity force is pulling down on all objects on Earth’s surface. If an object is
not falling there must be a gravity support force supporting the object
against the downward pull of the gravity force. This is the force that
balances gravity.
To measure gravity force we measure the gravity support force required
to keep the object from falling. Since the two forces are balanced to keep the
object from falling, the measure of the gravity support force is equal to the
gravity force.
We used a spring scale and mesh bag to measure the gravity support force
of a wooden sphere in the activity
Units of force are called newtons (n).
Weight is the measure of gravity pulling down on an object.
Mass is the amount of matter that an object contains.
Activity #3: Moving Masses
(pp. 4-5, 8, 12, 22)
Gravity Force pulls more strongly on objects that have more mass.
Acceleration is the rate of change in the speed and direction of an object.
Acceleration can mean speeding up, slowing down or changing direction,
Acceleration can be affected by both force and mass. Objects with a greater
mass will move slower than objects with a lesser mass and subject to the
same amount of force. The stronger the force on an object, the greater the
acceleration.
The steel ball and the wooden sphere hit the floor at the same time because
the gravity force on the steel ball was increased by its greater mass, while the
force created by book was greater on the wooden sphere because of its
smaller mass.
Newton’s Second Law of Motion states: an object acted on by a net force
will accelerate in the direction of the force. The object’s acceleration equals
the net force divided by the mass of the object
Activity #4: The Parachute Drop
(pp. 6-8)
Air Resistance is the force exerted by air against an object moving through it
and it acts in the opposite direction of the object’s motion. For example, an
object falling through air experiences an upward force of air resistance.
The flat piece of paper fell more slowly through the air than the crumpled
paper because it had a greater surface area and therefore experienced
greater air resistance.
Activity #5: Basketball Arcs
(P.23)
Gravity is always pulling down on an object in motion. This downward force
changes an object in motion’s horizontal path into a downward curve. This
curve is called a parabola. This motion can also be described as an arc.
Parabolas are not possible in space because of microgravity (free fall, the
almost weightless condition in the in-orbit environment).
Activity #6: Ball and Cup Contest
(p. 23)
According to Newton’s first law of motion, the ball on the end of the string
would continue to travel in a straight path until it is acted on by another
force. According to Newton’s second law an object moves in the direction of
the force that it experiences. Therefore the ball moves in the direction that
the string pulls on it. The result is a reaction to the 2 forces, a circular
motion.
In the activity, the inward force created by pulling on the string turned the
ball from it’s straight-line path.
This circular motion caused by the combination of two forces is called a
centripetal force.
Gravity has two effects on the ball and cup. It pulls the ball down into the
cup and keeps it in the bottom of the cup. In microgravity, the ball would hit
the bottom of the cup and according to Newton’s third law, experience an
equal reaction and bounce out of the cup.
Activity #7: Rolling On
(pp. 3, 6-7)
Friction occurs between a moving object and the surface on, or the medium
through, which it moves. It is a resistance force opposing motion. Friction
acts to reduce the speed of a moving object.
Speed is defined as the distance an object travels in a given amount of time.
Speed = distance/elapsed time that the object travels.
A rough surface produces more friction between a moving object that a
smooth surface.
The friction force is less for a rolling object than a sliding one.
Activity #8: Great Race
(pp. 3, 14)
Energy is an object’s ability to do work or produce change.
Kinetic energy is energy possessed by an object because of its motion.
Potential energy is energy possessed by an object because of its position.
Potential energy is stored energy.
As a car travels down a ramp it gains speed and kinetic energy. It also looses
potential energy. This concept of kinetic and potential energy being gained or
lost, demonstrates conservation of energy. Conservation of energy states
that, in a closed system, the amount of energy remains the same.
In the activity, the car had the greatest amount of potential energy at the top
of the ramp.
The car’s ability to increase its speed at the bottom of the ramp
demonstrated an increase in kinetic energy.
Activity #9: Accelerating Masses
(pp. 4-5)
Acceleration is the rate of change of speed and direction of an object in
motion.
Acceleration can be a speeding up or a slowing down.
Activity #10: The Come-Back Can
(p. 14)
Conservation of Energy- the total amount of energy in a system remains
constant, although it can be converted from one kind of energy to another.
When the rubber band in the system winds up, it stretches and thereby
stores potential energy. The system contains the greatest amount of
potential energy when the system is stopped and there is no evidence of
kinetic energy at work.
When the rolling can stops, the rubber band begins to unwind and as the can
begins to roll backward, the potential energy in the stretched rubber band is
converted into energy in motion, kinetic energy. The system has the
greatest amount of kinetic energy when it reaches its highest speed.
Therefore, the sum of the systems energy is always the same.
Activity #11:
Action-Reaction in Action
(p. 14)
Most motion on Earth’s surface depends on Newton’s Third Law of Motion:
Forces always occur in pairs. If object A exerts a force on object B, an equal
but opposite force is exerted by object B on object A.
An action force is exerted on an object- in the activity the ball exerts the
action force on the table.
A reaction force is the force exerted by the object that experiences the
action force- in the activity, the table exerts a reaction force on the ball.
The reaction force is equal to the action force but in the opposite direction.
Newton’s Law is sometimes stated this way: For every action force exerted
on an object, the object will exert an equal and opposite reaction force.
Activity #12:
The Grasshopper Game
(p. 13)
When we pushed down on the grasshoppers nose, the force from the push is
transferred to the table where the grasshopper is sitting. This is an action
force.
As the grasshopper pushes down on the table, the table pushes upward with
a reaction force and the grasshopper flips.
When we experimented with two different sizes of grasshoppers, the action
and reaction forces were the same for each grasshopper. However, because
one of the grasshoppers had less mass it was more affected by the forces and
was able to accelerate faster, and therefore traveled higher and farther.
Activity #13:
Clacker Conservation
One property of a moving object is momentum. Is not a force. It is an
indication of the force with which an object could act, for example, in a
collision. Momentum equals the mass of an object multiplied by its
velocity(p=m*v).
An object with a larger mass or higher velocity has more momentum and
could act with a greater force.
Conservation of momentum is when two objects interact only with each
other and the total momentum of the pair remains constant.
When one steel ball in Newton’s Cradle is pulled back and released, it is
mass in motion. When it collides with the stationary balls, that momentum
is passed along through the stationary balls to the last one, which is the only
one that can move freely. This last ball swings into motion with the velocity
imparted by the first. This process continues back and forth until the energy
of the system is lost to air resistance and friction.
Newton’s First Law of Motion- an object will remain at rest or in uniform motion
unless acted on by an unbalanced external force.
Newton’s Second Law of Motion- an object acted on by a net force will accelerate
in the direction of the force. An object in motion will accelerate at the same speed
and in the same direction unless acted upon by another force.
Newton’s Third Law of Motion- For every action force exerted on an object, the
object will exert an equal and opposite reaction force.