# Mechanics Study Guide Essay

1.1 If the Sun should suddenly explode (it can’t) how long would it take for us to notice the event? *

According to scientists we have at least 5-6 million years before the sun would ever die out or explode. However if a phenominon like that were to occur there are diffent theories to what might happen. It would take light from the explosion eight minutes to travel the 93 million miles from the sun to the earth. However, Newton’s Law of Gravity claims that Earth would suffer an immediate departature from its normal ellpitctal orbit. If this were to happen knowlege of the sun’s explosion would be instant due to the sudden change in the gravitational force conducting the Earth’s motion. 1.2 Convert the number of seconds in the day and the mass of the moon in kg, into scientific notation.

Seconds in a day: 8.64 × 10^4

Mass of moon : 7.34767309 × 1022 kilograms

1.3 Name Kepler’s’ three laws and state them in your own words.*

The Law of Ellipses:

“The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus.” This law reveals that every planet will revolve in an elliptcal orbit arround the sun and that they will remain in a bounded state.

The Law of Equal Areas:

“An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time.” This law implies that when a planet is far away from the sun moves slowly and moves faster when it is closer to sun.

The Law of Harmonies:

“The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. ” infers that if the planet is distant away from sun the time period of it around the sun is greater and when the planet is further away the time period around the sun is lesser. 1.4 What is the length (in AU) of the semi major axis of a body that takes 72 years (Halley’s Comet) to orbit the Sun?

17.8 AU

1.5 Suppose you were transported to a planet with 4 times the mass of the Earth but the same radius. Your weight would change by a factor of increase 2 fold? What if the mass were the same and the radius were four times larger. Your weight would change e by a factor of decrease 16 fold? 1.6 A robotic rover with a mass on Earth of 100 kg is transported to Mars. What is its mass and weight on its new home? (Hint: You will need to look up the gravitational acceleration on mars.)

Mass: 100 kg

Weight: 38

1.7 Name Newton’s three laws and state them in your own words. *

Newton’s first law states that “When viewed in an inertial reference frame, an object either is at rest or moves at a constant velocity, unless acted upon by an external force.This means that there is a natural inclination of objects to continue to do what they’re doing. All objects withstand changes in their state of motion. Without an unbalanced force, an object in motion will maintain this state of motion His second law states that “The acceleration of a body is directly proportional to, and in the same direction as, the net force acting on the body, and inversely proportional to its mass. Thus, F = ma, where F is the net force acting on the object, m is the mass of the object and a is the acceleration of the object.” This law implicates that heavier objects require more force to move the same distance as lighter objects. Newton’s third and final law tells us “When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body.” This law understands that for every force there is a reaction force that is equal in size, but opposite in direction. For example whenever an object pushes another object it gets pushed back in the opposite direction with an equal force.

1.8 What is the energy of a photon emitted from the surface of a star with a peak wavelength of 500 nm?(Plank’s Constant is 6.63 x10^-34 Js)*

E=hv

h = plank constant

v = nu = frequency = c/(wavelength)

c = speed of light = 300×10^6 m/s

h = 6.63×10^-34 J s

so for wavelength = 500 nm ->

E = 6.63×10^-34 J s * 500×10^6/(500×10^-9) = 663×10^-22 J

1.9 Describe the construction of a refracting telescope and a reflecting telescope. What is chromatic aberration? Which is used by professional astronomers and why? *

1.10 Name the 7 bands of the electromagnetic spectrum and give the ranges of frequency and wavelength for each. *