Friction? For example, like when a car's tires skid on rough concrete.
Answer:
hurricane.
Explanation:
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-- During the time the ball is flying from the high roof to the low roof,
it's going to fall (100-25) = 75 meters.
How long does it take an object dropped from rest to fall 75 meters ?
Distance = (1/2) · (gravity) · (time)²
75 m = (4.9 m/s²) · (time)²
Time² = (75 m) / (4.9 m/s²)
Time² = 15.31 sec²
Time = √(15.31 sec²) = 3.91 seconds
So the ball has to cover the horizontal distance of 20 meters
in 3.91 seconds.
Distance = (speed) · (time)
20 m = (speed) · (3.91 sec)
Speed = (20 m) / (3.91 sec)
Speed = 5.11 m/s
-- "Free fall" means no forces acting on the object except for gravity.
-- An object dropped through air has two forces on it -- gravity and air resistance.
-- So we're looking for the part of the drop where air resistance is smallest.
-- The force of air resistance depends on the speed through the air, so the
force of air resistance is smallest when <em>velocity downward is smallest</em>.
In order for an object to move, the forces acting on it must be ''unbalanced forces'' because balanced forces means equal canceling each other out so 0 to 0 while unbalanced means one side or thing is higher or lower than another and that makes objects move which are unbalanced since a side is not equal to the other.