YouTube Videos: Astronauts in Training . April 8 & 9. DO NOW – B DAY. Turn in your HW BOTH papers for big bang notes You have 10 minutes to review the following with your peers (make CORRECTIONS! You will see this stuff on next class’ test!)
April 8 & 9
#1 – 12 (ALL Movie notes except #9)
# 15 & 17
#18: a, c, d
#20 – 22
#30 – 32
WEIGHT is a measurement of the force of gravity between you and the planet on which you are standing…
BUT…how do you interpret it?
Pressure against Earth is the sensation we interpret as weight.
Rather than define your weight as the force of gravity that acts on you, it is more practical to define weight as the force you exert against a supporting floor; OR support force! According to this definition, you are as heavy as you feel.
The condition of weightlessness is not the absence of gravity (because gravity never goes away!), but the absence of a support force.
Look at the picture:
Both people are without a support force and therefore experience weightlessness.
**Astronauts still have GRAVITY acting on them…they just lack a SUPPORT FORCE**
What sensation do we interpret as weight?
From within a rotating frame of reference, there seems to be an outwardly directed centrifugal force, which can simulate gravity. *It does NOT create gravity…it just FEELS like it*
The centrifugal force experienced in a rotating reference frame is not a real force.
Real forces include: gravitational, nuclear, & electromagnetic.
Need for Simulated Gravity
Today we live on the outer surface of our spherical planet, held here by gravity.
What happens if we can no longer inhabit Earth?
In the future, people may live in huge,slowly rotating space stations where simulated gravity allows them to function normally.
Occupants in today’s space vehicles feel weightless because they lack a support force.
Future space travelers need not be subject to these feelings of weightlessness.
Their space habitats could spin, effectively supplying a support force and simulating gravity.
As seen from inside the rotating system:
Challenges of Simulated Gravity
The comfortable 1 g we experience at Earth’s surface is due to gravity.
Inside a HYPOTHETICAL rotating spaceship the acceleration experienced is the centripetal acceleration due to rotation.
Small-diameter structures would have to rotate at high speeds to provide a simulated gravitational acceleration of 1 g.
Sensitive and delicate organs in our inner ears sense rotation. Although there appears to be no difficulty at 1 RPM, many people have difficulty adjusting to rotational rates greater than 2 or 3 RPM.
*** Remember the ‘Vomit Comet’ video?**
To simulate normal Earth gravity at 1 RPM requires a large structure—one almost 2 km in diameter.
Rotation will allow people inside the space station to experience a support force that simulates normal Earth gravity.
A powerful set of analogies to examine size and distance in astronomy
QUESTION: At this scale, how far apart should they be?