KNEX Education Simple Machines Deluxe GEARS, Руководство для учителей

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Every gear has a job to do
A good way to visualize the need for a differential is to imagine a marching band making a turn.
The marchers on the inside of the curve don’t have far to go, so they take small steps and move slowly.
The marchers on the outside of the curve must move faster to keep the rows of marchers lined up. In a
front-wheel drive car, both front wheels are fixed to the axle, which is turned by the engine.
(The rear wheels receive the power in a rear-wheel drive car.)
The axle makes the wheels turn. Since both
wheels must be fixed to the axle, they must
use a differential to be able to turn at
different speeds.
Journal Ch
eck
✓
Description of how t
he Axle model works
and why
✓
Description of how t
he Axle with
Differential works an
d why
✓
Explanation of the m
ovement of the
Gears in the Differen
tial
✓
Description of the ac
tion of turning with
the Differential
✓
List of other machine
s that might benefit
from a differential
The Differential Lesson Plan
Materials
-carpet, towel or other rough
surface
Objectives
• Identify the type(s) of gear used in a differential
• Demonstrate how a differential functions
• Compare and contrast models with and without
a differential
• Understand the necessity of a differential in a vehicle
• Demonstrate how the planetary gears within a differential work
• Explain the advantage offered by these planetary gears and their
effect on force and speed
• Determine what other machines could benefit from a differential
Lesson Length:
30-45 minutes