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Gravity/Air Resistance
• THINK-PAIR-SHARE– What happened if you dropped two different
objects (meaning different masses) on the same planet?
– Did you already know this? What experience have you had that may have taught you this?
– Share with your partner.
• YES, it is true that if you drop two objects with differing masses they will hit the ground at exactly the same time.
• WHY?? – According to Newton’s laws, when an object is
accelerating it must have a force. For falling objects that force is gravity between the object and Earth
• Acceleration is due to the force of gravity.
• The force of gravity is 9.8 meters per second per second
• So for every second an object is falling its velocity is increasing by 9.8 m/s/s.
Mass and Weight
• Weight is a measure of the force of gravity on an object.
• How did you measure weight for this activity??
• Demonstration:
– Tennis ball and a pencil
PICK A GROUP OF 3 – Timer– Recorder/Observer– Dropper
• What did you observe during the demonstration? Why?
• Did the two objects hit the ground at exactly the same time? Why or why not?
Air Resistance
• Experience tells you that objects with different masses do not always hit the ground at the same time.
• The reason is air resistance, objects are pushed up by this opposing force. Eventually the forces become balanced and the object is no longer accelerating but it is moving at a constant velocity.
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