Download Notes – Free Fall and Acceleration at the Earth`s Surface ekb

Free Fall & Acceleration at the Earth’s Surface
All objects’ experience the force of gravity at the
Earth’s surface pulling them towards the center of
the Earth. This force results in an acceleration that
is called g.
a= g
The value is determined by the Earth’s Mass and
radius.
gEarth = 9.8 m/s2
gMars ≈ 3.77m/s2
gMoon ≈ 1.63 m/s2
gjupiter ≈ 25.95 m/s2
Free-fall is the motion of objects that move under the sole influence of gravity; freefalling objects DO NOT encounter air resistance.
ALL OBJECTS FREE FALL AT THE SAME RATE OF ACCELERATION,
REGARDLESS OF THEIR MASS.
**More massive objects will only fall faster if there is an appreciable amount of air resistance
present.
Free Fall
vi = 0
a=g
“g” refers to THE ACCELERATION DUE to Earth’s gravitational PULL!
*******IT IS NOT GRAVITY
All velocity and distance equations can be used by inserting g in for a.
v = at
d=
1
2
at2

v= gt

d= ½ gt2
Since acceleration is a vector quantity, it has a direction associated with it. The direction of the
acceleration vector depends on two things:


whether the object is speeding up or slowing down
whether the object is moving in the + or – direction
The general principle for determining the acceleration is:
When an object is speeding up, the acceleration is in the same direction
as the velocity.
When an object is slowing down, the acceleration is in the opposite
direction as the velocity.
The acceleration due to Earth’s gravity is actually NEGATIVE 9.8m/s2 (-9.8m/s2) –more on this
later…..
Acceleration Due to Gravity Comparison
Body
Mass [kg] Radius [m]
Sun
1.99 x 1030 6.96 x 108
Acceleration Due
g / g-Earth
to Gravity, "g" [m/s²]
274.13
27.95
Mercury 3.18 x 1023 2.43 x 106
3.59
0.37
Venus 4.88 x 1024 6.06 x 106
8.87
0.90
Earth
5.98 x 1024 6.38 x 106
9.81
1.00
Moon
7.36 x 1022 1.74 x 106
1.62
0.17
Mars
6.42 x 1023 3.37 x 106
3.77
0.38
Jupiter 1.90 x 1027 6.99 x 107
25.95
2.65
Saturn 5.68 x 1026 5.85 x 107
11.08
1.13
Uranus 8.68 x 1025 2.33 x 107
10.67
1.09
Neptune 1.03 x 1026 2.21 x 107
14.07
1.43
0.42
0.04
Pluto
1.40 x 1022 1.50 x 106