Space Physics: Space Travel
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what is newton's third law?
if A exerts a force on B, then B will exert an equal and opposite force on A
Newton's Third Law is saying that:
when you push on something, then, that something, whatever it is, pushes back on you
explain rocket motion in terms of Newton's Third Law.
- at lift-off, hot burning pas is pushed downwards by the rocket motors
- the hot gas pushes back on the rocket in an upwards direction
- when this upwards thrust exceeds the weight of the rocket, the forces acting on the rocket are unbalanced and the rocket accelerates upwards
what is the weight of an object?
the force on it due to the gravitational pull of gravity at that point.
what is weight measured in?
how does weight of an object differ on different plants?
the weight of an object on different planets is different from its weight on Earth.
What is the mass of an object?
the amount of matter that makes up the object and is measured in kilograms
how does the mass of an object differ on different plants?
it doesnt. the mass of an object remains the same no matter where the object is in the universe
what is the gravitational field strength of a planet?
its the weight per unit pass of an object on that plant.
what is the unit of gravitational field strength?
what is the inertia of an object?
a measure of how difficult it is to change its motion.
what effects inertia?
inertia increases for an object as its mass increases
what happens when an object is in freefall?
If you throw a ball up into the air as soon as you stop applying the throwing force it is being accelerated down. This is due to the gravitational field strength of the Earth
when an object is in freefall, what does it appear to be?
what is projectile motion?
When an object is projected horizontally in a gravitational field it will follow a curved path
why does projectile motion occur?
- the only force acting on the object is the force due to gravity acting vertically downwards.
- This results in a constant downward acceleration.
- there are no horizontal forces so the object continues to move with a constant horizontal speed
what is the equation for horizontal motion?
d = vt
what is the equation for vertical motion?
v = u + at
what is an example of projectile motion?
how a satellite orbits the Earth
what is necessary for the Space Shuttle to stay in orbit?
it cannot simply go straight up into space but curves on its back so that when it reaches the desired orbital height it is travelling at an extremely high speed horizontally
what the the approximate horizontal speed that the International Space Station orbits the Earth at?
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