Motion · Topic 2 of 17

Acceleration & Free Fall

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Physics · motion

Acceleration is change in velocity divided by time, in m/s². In free fall every object accelerates downward at g = 9.8 m/s², whatever its mass.

01 · Accelerationa = Δv ÷ t (m/s²)

02 · Gravityg = 9.8 m/s² downward

03 · The trapAt the top: v = 0, a = 9.8 m/s² down

Acceleration = any change in velocity (speed, direction, or both) must know

Free fall: gravity only, same g for every mass must know

Dropped from rest: v = gt, distance fallen = ½gt²

Up positive → a = −9.8 m/s²; down positive → a = +9.8 m/s²

Free fall includes going up — loses 9.8 m/s each second rising

a = (v_final − v_initial) ÷ time, in m/s² must know

g = 9.8 m/s², pointing down must know

v = v₀ + at (final velocity)

x − x₀ = v₀t + ½at² (from rest: d = ½at²)

No time given? v² = v₀² + 2a·Δx

4 → 22 m/s in 6 s: a = 18 ÷ 6 = 3 m/s²

Dropped 3 s: v = 9.8 × 3 = 29.4 m/s; d = 4.9 × 9 = 44.1 m

Up at 14.7 m/s: top after 1.5 s, at ≈ 11.0 m

Commonly confused

Deceleration = acceleration opposite the motion (negative ≠ always slowing)

At the top: velocity = 0, acceleration still 9.8 m/s² down

Air resistance, not mass, makes light objects fall slower

Show 2 more facts

Constant a: average velocity = (v₀ + v) ÷ 2

g varies slightly: about 9.78 to 9.83 m/s²

Pearl

Thrown up or dropped, a falling object's acceleration never changes: 9.8 m/s² down, even at the very top.

Practice this topic, then test the whole section.

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