### 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

### Why?

-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

### Why?

-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?

-yes

-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

### Why?

-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...?

-m