Space Flashcards
What is weight?
The weight of an object is the force experienced by that object due to the presence of a gravitational field
What is weight mathematically?
Weight is measured in newtons and is the mass of the object multiplied by the acceleration due to gravity
What path does a projectile take on earth?
A parabola
What are the two components of projectile motion and how are they analysed?
Vertical and horizontal components and they are analysed independent of one another
What happens to the x component of velocity throughout projectile motion?
It remains constant
What we’re Galileo three main ideas regarding projectile motion?
- All projectiles follow a parabolic path
- Regardless of mass all objects on earth fall at the same rate
- Horizontal and vertical components of velocity are independent of each other
How did Galileo reach the conclusion that all objects accelerate toward the earth at the same rate and that the time and distance travelled have a square relationship?
By developing an experiment involving rolling balls of different masses down a highly polished ramp to make his comparisons. This would allow him to slow down the motion enough to make more accurate observations of the motion, as compared to just dropping balls to the ground
How did Galileo reach the conclusion that projectiles follow parabolic paths?
By rolling balls off a table at different speeds and mapping the motion
How did Galileo reach the conclusion that projectiles in motion express horizontal and vertical components which are independent of each other?
By coming up with a thought experiment we’re a rider of a horse drops a ball in front of a stationary observer
- according to the rider, the ball drops straight down
- according to the stationary observer, the ball travels with the same horizontal velocity as the rider
What is escape velocity?
The velocity required at a planets surface to completely leave its gravitational field without further energy input.
In terms of kinetic and gravitational potential energy, what does escape velocity represent?
The limiting case where the projectile ‘just reaches infinite displacement’ with zero speed.
In other words, a projectile must have the same amount of kinetic energy as the absolute value of the gravitational potential it has at take off.
That is , kinetic energy + gravitational potential energy is greater than or equal to zero
What did newton use to explain the concept of escape velocity?
Newton came up with a thought experiment where a cannon fires a projectile horizontally on the earths surface with no air resistance.
- at first the projectile would follow a parabolic path and hit the ground some time later
- as speed increases, it will take progressively longer for the projectile to hit the ground, because although gravity is pull the projectile in toward the centre of the earth, the earth is also falling away from the object at the same rate due to its horizontal motion
- increase the speed once more and the projectile with never hit the ground and follow a circular orbit around the earth
- increase it even more, the orbit forms and ellipse
- finally increase more and the projectiles motion becomes hyperbolic and it escapes the earths gravitational field.
What are g forces?
Refers to the force experienced by an astronaut in terms of the earths gravitational field on the surface
What are the two forces acting on an astronaut during launch ?
- the upwards thrust T caused by the rocket
- his/her own weight W acting towards the centre of the earth
By Newton’s second law, what is Thrust equal to?
T= ma + mg
Thus
T-mg = ma
What is thrust equal to in a rocket launch?
The apparent weight of the astronaut, by Newton’s third law
What is the formula of g force?
1 + a/g
Apparent weight/real weight
Why are astronauts put into reclined seats during rocket launch?
They are placed in a position which concentrates the force perpendicular to their long body axis, placing it at their backs, which is good because it prevents black out and red out.
Why do astronauts have specially moulded seats?
Increases the surface of the forces
Why is the term g force used?
It’s easy to relate to and it eases calculations regarding the forces experienced by astronauts during launch
What does the law of conservation of momentum state?
The law of conservation of momentum states that in a closed system, the sum of momenta before a change is equal to the sum of momenta after the change
what is gravitational potential energy?
defined as the work down to move an object from a very large distance away to a specific point in a gravitational field
why is gravitational potential energy always negative?
if an object is lifted above a planets surface, work is being done on that object, giving it energy. if energy is given to the object, its gravitational potential energy must increase. but, at an infinite distance away from the plant, the potential energy is zero. so thus this means that it is a bound system and at the planets surface the GPE of the object will be its lowest possible value
what was the michelson morley experiment and what was its aim?
the michelson morley experiment was designed to calulate the velocity of the earth through the aether, on the grounds that light would travel faster in certain directions and slower in others, due to the relative motion between the earth and aether which could create an Aether wind