Transcript Falling and Air Resistance - Fort Thomas Independent Schools

Falling and Air Resistance
Reading Guide Answers
Chapter 6.7
Falling and Air Resistance
• 1. The accelerations of the feather and coin in a
vacuum (no air) are the same. This would be no
different on the moon, because the Moon has no
air resistance. However, since the moon has
less gravity, they would both fall slower than on
Earth.
• 2. As the air resistance increases, the net force
will decrease. (or as the air resistance
decreases, the net force will increase)
Falling and Air Resistance
• 3. The net force of an object in free fall is equal
to the weight of the object (air resistance is not
considered in free fall)
• 4. Air resistance is dependent upon
– A.
– B.
speed
frontal area: exposed surface area
• 5. Air resistance can be reduced by
– A.
– B.
reducing speed
reducing frontal area (exposed surface area)
Falling and Air Resistance
• 6. The elephant would experience more
air resistance because the elephant has a
much larger frontal area exposed to air.
The elephant
catches more air!
Terminal Velocity
• 1. Terminal speed is the maximum speed that a
falling object will reach; it occurs when the
acceleration and net force equal zero. Terminal
velocity differs only by the addition of direction of
motion (down!)
• 2. Weight (gravitational force) and air
resistance balance at terminal velocity.
• 4. A feather reaches terminal velocity so quickly
because its frontal area is very large compared
to its very small weight.
• 5. Terminal velocity for a skydiver ranges from
150 to 200 km/h. (124 mph)
• 6. Zero acceleration means that the object is no
longer accelerating; zero velocity means the
object is at rest.
• 7. Terminal speed changes if the frontal area
exposed to the air changes (variations in body
orientation). If the skydiver reduces frontal area,
the terminal speed would increase. If the
skydiver increases the frontal area, the terminal
speed would decrease.
• 8. Terminal velocity for a skydiver with the
parachute deployed ranges from 15 to 25 km/h.
• 9. As the baseball and tennis ball fall, their
speeds will increase and the air resistance
builds. Since the weight of the tennis ball is less
than the baseball, the net force on the tennis ball
decreases more quickly than the net force on the
baseball. This causes the falling tennis ball to
be accelerated at a progressively lower rate than
the falling baseball.