the gravitational force · the gravitational field the gravitational field at any point in space...
Post on 14-Jul-2020
3 Views
Preview:
TRANSCRIPT
The Gravitational Force
What Factors Affect the Gravitational Force?
What Did You Learn?
What is the relationship between F1 and F2?
They are equal in magnitude but opposite in direction.
These forces are a Newton’s Third Law Pair!
What Did You Learn?
What type of relationship is there between Fg and m1?
Proportional!
The gravitational force increases!
What happens as mass 1 increases?
What Did You Learn?
What type of relationship is there between Fg and m2?
Proportional!
The gravitational force increases!
What happens as mass 2 increases?
What Did You Learn?
What type of relationship is there between Fg and m1?
Power!
The gravitational force decreases!
What happens as distance increases?
What Did You Learn?
Does your equation look like this?
Fg = constant * r-2
Fg = constantr2
What does that mean?
Creating a Mathematical Model
Fg = constantr2
Fg = constant * m1
Fg = constant * m2
Fg =constant *m1m2
r2
Because we are talking about gravity, the constant is represented by the letter G!
Fg =Gm1m2
r2
What’s the Attraction?Gravity is known as the weakest of the fundamental forces.
Let’s see how strong it actually is on an everyday level!
What is the force of gravity between a loving couple standing 30 cm apart
if one has a mass of 60 kg and the other has a mass of 75 kg?
Fg =Gm1m2
r2
Fg = 3.3 x 10-6 N
If the dance floor is frictionless, how long would it take them to reach each other?
What’s the Attraction?
xf = 1/2at2 + vot+ xo
If the dance floor is frictionless, how long would it take them to reach each other?
xf = 1/2at2
a = F/m
Minnie: a = 3.3 x 10-6 N/60 kg
Mickey: a = 3.3 x 10-6 N/75 kg
a = 5.5 x 10-8 m/s2
a = 4.4 x 10-8 m/s2
xf = 1/2at2 + 1/2at2
xf = 0.30 m
t = 2462 s = 41 min
Falling Apples
Newton developed this mathematical relationship.
A falling apple is experiencing the same force as the moon orbiting the Earth!
What is G?A scientist named Cavendish was trying to figure
out the internal structure of the Earth.
Designed an experiment to determine the Earth’s mass.
G = 6.67 x 10-11 Nm2/kg2
Weighing the Earth
Let’s say you have an apple in free fall.
Fg = maag
Fg =GmamE
r2
maag =GmamE
r2
ag =GmE
r2
Weighing the EarthIf the apple is near the Earth’s surface, then the distance
between the apple and the Earth is the Earth’s radius.
ag =GmE
r2
mE =r2ag
G
Units must be in kg, m, and s!
mE = 5.96 x 1024 kg mE = 5.98 x 1024 kg
What’s the Free fall Acceleration?Jupiter’s moon, Io, has a mass of 8.93 x 1022 kg and has a
diameter of 3630 km. What is the acceleration due to gravity on an object in free fall at Io’s surface?
ag =GmI
r2
Info:
ag = 1.8 m/s2
mI = 8.93 x 1022 kg
r = 1,815,000 m mo = ?
ag = ?
moag =GmImO
r2
The Gravitational FieldThe gravitational field at any point in space is defined as the
gravitational force felt by a tiny unit mass placed at that point.
g is known as the gravitational field. The magnitude of g is…
g = Fm
g = GMr2
Multiple ForcesObjects can experience multiple forces of gravity at once.
The tides are caused by the gravitational pull of the
Moon on the Earth.
Spring tides occur twice a lunar month and are caused when the Earth, Moon, and Sun are all aligned.
It is important to remember that the gravitational equation only gives you the magnitude of the force!
You will need a free-body diagram to determine the direction!
Spring TidesmE = 5.98 x 1024 kg
mM = 7.35 x 1022 kg
mS = 1.99 x 1030 kg
rES = 149.6 million km
rEM = 384,400 kmFEm
FES
FEM =GmmmE
rEM2FES =
GmSmE
rES2
The gravity equation can only look at two objects at a time!
Fg = FEM + FES
Fg = 1.98 x 1020 N + 3.54 x 1022 N = 3.56 x 1022 N
Unit 4C - Problem Set
Topic Sections Questions
Force of Gravity 4.7 20, 23, 24, 25, 28
Uniform Circular Motion 5.1-5.3 1, 2, 13, 19, 23
Satellites and Orbits 5.5 & 5.6 32, 36
Vertical Circular Motion 5.7 42, 45, 60
Things To Remember When Completing Your Problem Set!
A picture can illustrate the situation or be a free-body diagram!
top related