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.