Transcript Lessons 7 and 9 Notes - Nutley Public Schools

Lessons 7 and 9 Notes
“Rolling Along” and “The Fan Car”
1. The force of the roll is
the unbalanced force
that gets the ball rolling.
1. Inertia allows the ball to
keep rolling.
3. There is friction acting between
the ball and the ground allowing it
to roll instead of slide.
• Newton’s Second Law
of Motion: Acceleration
is produced when a
force acts on a mass.
• The fan is the force that
causes the fan car to
move forward.
Lesson 7: “Rolling Along”
• In this inquiry, we rolled a steel ball across the
classroom and we measured the average speed.
Distance Traveled
Average Speed = _______________________
Time
The units for average speed for these inquiries
are meters/seconds or m/s.
Forces Acting on the Steel Ball:
• The unbalanced force acting on the steel ball to
move it forward was the force of the roll.
– Friction was the force between the ball and the
ground.
– Gravity was the force that kept the ball on the
ground.
Newton’s First Law of Motion: An object in
motion stays in motion unless acted on by an
unbalanced force. An object at rest stays at rest
unless acted on by an unbalanced force.
• Newton’s First Law of Motion is also known
as the “Law of Inertia”.
• Inertia is what keeps the steel ball in motion
after it has been rolled.
Examples of Newton’s First Law of Motion:
• The Steel Ball (Lesson 7) – The steel ball will
stay in motion until it hits a wall (unbalanced
force).
• The Fan Car (Lesson 9) – The fan car will not
move until the fan (unbalanced force) is turned
on.
Kinetic Energy is energy associated with moving
objects. The steel ball and the fan car have
kinetic energy.
Kinetic Energy = 1/2mv2
An increase in mass or
speed will cause an
increase in kinetic
energy.
Kinetic Energy =
(1/2 x mass) x (velocity)2
Kinetic Energy is measured in
Joules (J).
Example Problem:
If the mass is 4 kg and the velocity (speed) is 1.8 m/s. What is the kinetic
energy?
Step 1: Multiply the mass by ½.
Step 1: ½ x 4 kg = 2 kg
Step 2: Square the speed.
Step 2: (1.8)2 = 1.8 x 1.8 = 3.24 m/s
Step 3: Multiply the two answers together.
Step 3: 2 kg x 3.24 m/s =
Step 4: Record your answer in Joules (J).
Step 4: 6.48 J
Lesson 9: “The Fan Car”
• In this inquiry, we used the fan car with the fan off and with
the fan on to see the change in motion/speed.
• Fan Off: The unbalanced force moving the car forward is
the student pushing it. The motion of the car was quick
immediately after the push but then slowed down and
eventually stopped because friction was acting on the car.
– Hard Push – the car went faster for a longer distance.
– Soft Push – the car went slower and did not go as far.
• Fan On: The unbalanced force moving the car forward is
the fan. The motion of the car increased in speed over time.
The car did not stop until it hit something or until the fan
ran out of energy (batteries).
Forces Acting on the Fan Car:
• Friction is working between the car’s wheels
and the floor.
• Gravity is keeping the car on the ground.
• Air resistance is going in the opposite direction
to the motion of the car.
Newton’s Second Law of Motion: Acceleration
is produced when a force acts on a mass.
Example of Newton’s First Law of Motion:
• When the fan (force) was turned on, the car
(mass) moved forward (accelerated).
• Basically the force of the fan caused the car to
move out of rest and into motion, which is a
change in speed (acceleration).