ENGAGE Let the students imagine that they are inside a dark, cold room in a winter night. Ask them, ‘ What ■as the best way to keep the hands warm?" EXPLORE ^c e d u re : Predict what will happen when you rub hands together vigorously. I
Rub your hands together. Do your hands feel warmer?
3
Rub your hands together again faster and longer. Put your hands on your face.How do your hands feel? Run water on your hands and see if it rubs the same. Now add lotion to dry hands and rub them again. Do you feel a difference in the amount of heat? t
EXPLAIN
Classroom Discussion about Gravity and Friction Gravity •
Gravity is a force that always attracts or pulls objects toward each other without direct contact or impact.
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Gravitational attraction depends on the mass of the two objects and the distance they are apart.
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Objects on Earth are pulled toward the center of Earth.
Friction •
It is a force that occurs when one object rubs against another object. Two factors that determine the amount of friction:
•
1.
The kind of surfaces
2.
The force pressing the surfaces together
Friction is the force that acts to resist sliding of two surfaces that are touching. It can slow down or stop the motion of an object.
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The smoother the two surfaces are, the less friction there is between them; therefore, the moving object will not slow down as quickly.
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The greater the force pushing the two surfaces together, the stronger friction prevents the surfaces from moving.
UNIT III: INSTRUCTIONAL STRATEGIES FOR SCIENCE
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