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Level 110

Gravitation


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Gravitational Force
(physics) the force of attraction between all masses in the universe
Law of universal gravitation equation
F = Gm₁m₂/r², where F is the gravitational force, m₁ and m₂ are the masses and r is the distance between their centres.
Universal gravitational constant, G
G = 6.67 x10⁻¹¹ N kg⁻² m²
Gravitational field strength, g
The force per unit mass placed at that point in the field
Uniform gravitational field
A constant field strength with parallel, equally spaced lines of force
Radial gravitational field
A varying field strength around a spherical object that reduces with distance away from the centre.
Gravitational field strength equation
g = GM/r², where g is the gravitational field strength, G is the universal gravitational constant, M is the mass causing the force and r is the distance between centre of the field and the mass in the field.
Gravitational potential, V
The work done in bringing a unit mass from infinity to a specific position in a gravitational field.
Gravitational potential equation
V = -GM/r, where V is the gravitational potential per unit mass, G is the universal gravitational constant, M is the mass causing the field and r is the separation of the objects' centre
Equipotentials
Lines of constant potential where all points at the same height have the same gravitational potential. The more spaced out the lines the weaker the field.
geocentric
earth-centred
heliocentric
sun-centred
empirical
drawn from observation rather than from laws already known
law of orbits/Kepler's First law
the orbit of every planet has the shape of an ellipse
foci
points about which an ellipse is drawn
law of areas/Kepler's Second Law
the line connecting a planet to the sunsweeps out equal areas in equal times
law of periods/Kepler's third law
For any planet, the square of the period of revolution about the sun is proportional to the cube of the average distance from the sun; T² = Cr³
kinematics
branch of mechanics that explains the "what" and "how" of motion
Dynamics
A branch of physics that focuses on force and how they relate to motion.
F = Gm₁m₂/r²
universal law of gravitation
constant of gravitation
G; 6.673 × 10⁻¹¹ N·m²/kg²; 3.435 × 10⁻⁸ lb·ft²/slug²
gravitation
the attractive force that exists between masses
gravity
(physics) the force of attraction between all masses in the universe
r, the distance between two objects
any two objects attract each other as if the mass of each were concentrated at its center of mass
Cavendish balance
a balance with two small lead spheres connected to the ends of a thin rod, which is suspended on a quartz fiber; light shining on a mirror attached to the fiber is reflected …
free fall
a state in which an object is gravitationally drawn to the earth's surface and is unaffected by any forces besides weight
Terminal Velocity
Greatest velocity an object can reach is called _______.
cogitation
thinking deeply, relying solely on whatever facts or insights you can discover within your own mind
observation
the careful watch and recording of events in nature for the purpose of enlarging what you already know
experiment
The components of the rate law, reaction orders (m & n) and rate constant (k), must be found by...?
scientific method (1)
formulation of question
scientific method (2)
search of the scientific literature for other work relating to the same question
scientific method (3)
consideration of all the facts available
scientific method (4)
formulation of an hypothesis
scientific method (5)
design of an experiment
scientific method (6)
performance of an experiment
scientific method (7)
analysis of the procedures and results
scientific method (8)
preparation and publication of a report to other scientists
Stable Equilibrium
An object is perturbed from equilibrium and returns to equilibrium.
unstable equilibrium
state in which an object is upset at the slightest disturbance; since the net force on an object in unstable equilibrium is zero, the object maintains its precarious balance indefinitely if protected from any disturbing force
neutral equilibrium
state in which an object may be overturned without changing the height of the centre of gravity
unstable object
an object that is subjected to the unbalanced force of weight, and, thus, falls immediately unless provided with support
metacenter
the point of the axis of symmetry directly above the center of buoyancy of a water-bourne object
multiple suspension
hanging an object at each of various points along the edge and drawing a vertical line with the help of a plumb line
centre of mass (CM)
a point at the centre of gravity; it has meaning even when the CG, which is exactly the same point, has none
critical velocity
the horizontal velocity a projectile must attain to go into orbit
Escape Velocity
Square root: 2GMc/r
Gravitational Field Strength
gravitational force per unit mass experienced by a mass placed at that point
Newton's Law of Universal Gravitation
Every particle in the universe attracts every other particle with a force that is directly proportional to the product of the masses and inversely proportional to the square of the distances between their centers
inverse square law
a quantity varies with the inverse square of its distance from its source
Universal Gravitational Constant
F=g(m1m2/r^2) G = 6.67 E-11 N m² / kg²
0
0
Orbit
Is a curved path that objects follow when influenced by large gravitational bodies such as planets or stars.
stronger
The darker the color of the solution the _______ the concentration.
mass and distance
What are the two major factors that determine the strength of an object's gravitational pull?
Sun
Example of a luminous object
9.8 m/s^2
Acceleration of objects due to gravity on Earth
Isaac Newton
A man from England who realized that the planets move around the Sun because of inertia as well as developing the laws of motion and gravity
Who is Copernicus?
Founder Heliocentric Model of the solar system
Studied Jupiter's moons.
Who is Galileo Galilei?
Who is Tycho Brahe?
Measured the position of the 5 known planets.
Who is Johannes Kepler?
Kepler's three laws of planetary motion.
What are the three laws of Kepler?
Law of Orbit, Law of Area and Law of Period
What is the law of orbits?
The orbits of the planets are ellipses with the sun at one focus.
What is an ellipse?
The set of all points whose combined distances to two fixed points is constant.
What is eccentricity?
measure of how elongated an ellipse is.
What is the law of areas?
The line joining a planet to the sun traces out equal areas at equal times.
What is the law of periods?
The square of the period of the planet is proportional to the cube of its average distance from the sun.
t^2 = k r^3
The formula of the law of periods
Who is Isaac Newton?
The founder of gravity.
What is the universal law of gravitation?
all objects pull on other objects in a simple way that involves only their masses and distances.
f = GMm/r^2
Formula of force of gravity
Henry Cavendish
A British physicist and chemist whose most famous experiment used a torsion bar to determine the value of the universal gravitation constant to determine the weight of the earth
6.67 x 10^-11
G is equal to
5.98 x 10 ^24 kg
What is the mass of the Earth?
Is g equal to G?
No, g is the acceleration due to gravity and G is the gravitational constant.
What is the gravitational force?
The force of gravity that the Earth exerts on a person.
The gravitational force.
What is true weight?
What is apparent weight?
The force that the person exerts on the ground.
What is normal force?
Is the upward force of the ground on the person.
What is Apparent weightlessness?
In free fall, when an object has the lack of a support force, and therefore feels like it is weightless
What is true weightlessness?
There is no effect of gravity.
What is a tide?
The periodic changes in sea level due to the gravitational interaction of the Earth, Moon and Sun.
Four
How many tides per day?
What is a spring tide?
High high tides and low low tides.
What is a neap tide?
Low high tides and high low tides.
Why doesn't the sun affect the tides more than the moon since its force is 180 times greater?
Because tides are caused by the difference in gravitational force at opposite sides of the Earth. Due to the inverse square law.
What is the inverse square law?
The force of gravity gets weaker with the square of the distance between two objects.
Action-at-a-distance theory
Field was originally named
What is a gravitational field?
A force field that exists in the space around every mass or group of masses
What is gravitational field strength?
Measures how strong the field is at a point.
How to measure the field strength?
By placing a small test mass.
g =
gravitational force / test mass
the procedure for finding acceleration
The procedure for finding g is equal to
What is gravitational shielding?
The ability of an object or material to block the gravitational force and keep it from reaching an object.
The inverse square law applies to
brightness of light and loudness of sound
Zero. Pulled equally in all directions.
What is the gravitational force at the center of a sphere?
Zero.
What is the gravitational force in/around a hollow sphere?
NOT zero. Proportional to the objects distance from the center
What is the gravitational force off center in/around a solid sphere?
What is escape velocity?
The minimum speed an object needs in order to escape the gravitational field of a planet.
11.2 km/s
Earth with respect to own gravity
The stronger gravity is the
bigger the escape velocity has to be.
What is a black hole?
A shrinking planet whose gravity increases immensely.