## ii- Free Fall

Free Falling

“Free fall acceleration”
“Acceleration due to gravity”

• If you drop a rock and a feather in an air-filled tube, the rock reaches the bottom first, this is due to the presence of air resistance (the feather is slowed much more by the air).
• In an evacuated tube (no air inside), in absence of air resistance, both the rock and the feather have the same acceleration. They will reach the ground at the same time.
• The acceleration due to gravity us denoted by the symbol g. g is a vector.

g = 10 m/s2 = 10 N/kg

Important Notes:-

a-   The acceleration of free fall for a body near to the Earth is constant.

b-   As we go upwards, leaving the earth’s surface, the value of (g) acceleration due to gravity decreases, till we reach away space g=zero.

Graph of free falling Acceleration due to gravity [g] in going up and down

Speed increases as going down with constant acceleration.

Speed increases 10 m/s each one second so acceleration due to gravity is approximately
g =10 m/s.

Speed decreases as going up with constant acceleration

Speed decreases 10 m/s each one second
So acceleration due to gravity is approximately 10 m/s, but since we are going up, you can use g = -10 m/s2