Describe the movement of the moon towards the earth
-the moon is constantly falling towards the earth
Describe the movement of an object in uniform circular motion in relation to the center of the circle
-an object in uniform circular motion accelerates toward the center of the circle
What is the force responsible for the moon's centripetal acceleration?
-the Earth's gravitational attraction
Comparatively describe the force that each mass experiences
-each mass experiences a force of the same magnitude, but acting in opposite directions
What is one of the key implications of the law of universal gravitation? (hint: related to attraction between objects in the universe)
-all objects in the universe attract all other objects in the universe by way of gravitational interaction
What does the fact that G is such a small number mean?
-that the force of gravity between objects of human proportions is imperceptibly small
Does the force of gravity ever vanish with distance?
-no it does not
-gravity is a force of infinite range
Since F varies as 1 / r^2, what is F said to have?
-F is said to have an inverse square dependence on distance
For example, an increase in distance by a factor of 10 results in a decrease in the force by a factor of what?
10^2, or 100
Since the force of gravity between two masses depends on the product of the masses, what follows? (in terms of gravity)
-that if either mass is doubled, the force of gravity is doubled as well
If a given mass is acted on by gravitational interactions with a number of other maseses, what is the net force acting on a mass?
-a vector sum of each of the forces individually
Does the acceleration due to gravity have a higher value at sea level or on the top of Mt. Everest?
-higher value at sea level
Does the universal gravitation constant to Mars? to the Moon?
-yes, the universal gravitation constant applies to any object in the universe
What is the distance of the "r" value that is used in Newton's Law of Universal Gravitation?
-the distance between two massess center-to-center
What does the universal gravitation law actually say?
-if you take two 1 kg masses and put them 1 meter apart, then the strength of the attraction is equal to 6.67e^-11 N * m^2 / kg^2
What is one of the most important implications of G?
-every object in the universe is attracted to all other objects
-F of gravity will not equal zero unless r = infinity
-since the universe is not infinite, the case will never be met
-->thus, every object in the universe will always be attracted to other objects
If we experience attraction to everything in the universe, why do we only feel one attractive force (to that of the Earth)?
-because Earth is the biggest mass that is close by
-if you were to go inside of a body, you would have different parts of a body pulling on you differently
Therefore, what impact does increasing the mass of an object have?
-if you increase the mass of an object (while your location stays the same), then weight will correspondingly increase
If you traveled from the Earth to the Moon (and ate a typical/healthy amount on the way), would your mass stay the same?
-mass is an intrinsic property that is not dependent upon location
If you traveled from the Earth to the Moon (and ate a typical/healthy amount on the way), would your weight stay the same?
-no it would not
-because weight is an extrinsic property that is dependent upon location
-since the moon's gravitational force is less than that of the Earth's, weight will decrease when mass is held constant
Therefore, what is the relationship between kilos and pounds?
-1 kg of mass only weighs 2.2 lbs on the Earth's surface
-comparison values will be dependent upon location
When an object is in orbit around another body, how does the force required to keep the object in circular motion compare to the actual force supplied?
force required = force actual
Describe the relationship between orbital speed and distance
-as the distance between two object increases, the necessary orbital speed decreases
-->as you go farther away, you can slow down and still maintain circular motion
Describe the moon's position when it is not visible in the sky
-the moon is between the Earth and the sun
-as such, it is not illuminated from our perspective and we cannot see it
Describe the moon's position when it is "half moon"
-moon and Earth at an equal x distance from the sun
-as a result, only half of the moon is illuminated by the sun from our perspective
Describe the moon's position when it is full moon
-Earth is between moon and sun
-all of moon is illuminated from our perspective
The orbital period of the moon around the Earth is calculated to be 27.4 days. Why is the actual period greater than this value?
-as the moon is travelling around the Earth, after 27 days the Earth has changed position
-when the Earth's movement is accounted for, the phases of the moon are more than one Earth period
What has been instituted to ensure that we do not develop further inaccuracies?
-currently, we do not have a leap year every year
-leap years do not occur during turn-of-century years that are not divisible by 400
It is often said that astronauts in orbit experience weightless ness because they are beyond the pull of Earth's gravity. Is this statement correct? Explain.
-no it is not
-->the force of Earth's gravity is practically as strong in orbit as it is on the surface of the earth
Why can't gravitational force be dependent upon the sum of two masses?
-because it would predict a nonzero force even when one of the masses is zero
-->this is certainly not observed
An astronaut orbits the Earth in a space capsule whose height above the surface is one Earth radius. If m is her mass on the surface of the Earth, then at her current location, her mass is...?