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Free Fall. Fall due to gravity Acceleration of an object in free fall = gravitational acceleration = g A free falling object’s speed increases by 9.8 m/s (≈ 10m/s) every second ( u pward +; downward ‒) Air resistance negligible. Upward displacement = “+” Downward displacement = “–”.
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Free Fall • Fall due to gravity • Acceleration of an object in free fall = gravitational acceleration = g • A free falling object’s speed increases by 9.8 m/s (≈ 10m/s) every second (upward +; downward ‒) • Air resistance negligible
Upward displacement = “+” Downward displacement = “–”
Gravitational Acceleration, g • If upward is defined as the positive direction, then –g (and +v) • When the object is coming down, –g (and –v) • The velocity at the moment of reversing direction = 0 • If downward is defined as the positive direction, then +g (and +v)
Formulas with g • displacement: • velocity: • acceleration:
Example A rock is thrown upward with a speed of 26 m/s. How long after it is thrown will the rock have a velocity of 48 m/s toward the ground?