A, C, and D all happen at different stages
of a total lunar eclipse.
I'll describe the stages of the eclipse, but before I do, I just need
to clarify: The Earth doesn't have an umbra or a penumbra, but
its shadow does.
-- the eclipse begins when the first edge of the moon
moves into the penumbra of Earth's shadow; ( C )
this part of the moon grows steadily.
-- After a while, the first edge of the moon begins to move
into the umbra of Earth's shadow ( A ), and gets very dark.
-- The total phase of the eclipse begins when the ENTIRE
moon is in the umbra of Earth's shadow.
Then everything happens in reverse.
-- Eventually, the leading edge of the moon moves out
of the shadow's umbra, into the penumbra. This part
steadily grows.
-- After a while, none of the moon is in the umbra, and
the whole thing is in the penumbra. The moon is
fully illuminated, but not quite as bright as it should be.
-- Soon, the leading edge of the moon leaves the penumbra
of Earth's shadow, and gets brighter. This portion of the moon
steadily grows, until ...
-- the moon completely leaves the penumbra, all of it is as bright
as it's supposed to be. The eclipse is completely over. ( B )
==> The whole process lasts several hours.
==> Everybody on the night side of the Earth sees the same thing
at the same time. It doesn't matter WHERE you are on the night
side ... if you can see the moon in the sky, you see the present
phase of the eclipse.
==> The lunar eclipse can only happen at the Full Moon. In fact, the
mid-point of the total phase is the exact moment of Full Moon.
Answer:
(a) 1767.43 N
(b) 182.45 N
Explanation:
Radius of earth, R = 6450 km
Weight of person, W = 7070 N
mass of person, m = W / g = 7070 / 9.8 = 721.4 kg
(a) h = 6450 km
The value of acceleration due to gravity on height is given by
g' = g / 4 = 9.8 / 4 = 2.45 m/s^2
The weight of the person at such height is
W' = m x g' = 721.4 x 2.45
W' = 1767.43 N
(b) h = 33700 km
The value of acceleration due to gravity on height is given by
g' = g x 0.0258 = 9.8 x 0.0258 = 0.253 m/s^2
The weight of the person at such height is
W' = m x g'
W' = 721.4 x 0.253
W' = 182.45 N
My guess would be choice D
Answer:
Sound waves transfer energy by causing successive compressions and rarefactions in the particles of the medium without transporting the medium particles themselves. Sound in solids can also manifest as transverse waves, causing crests and troughs in the propagation medium.
Answer:
0.47 N
Explanation:
Here we have a ball in motion along a circular track.
For an object in circular motion, there is a force that "pulls" the object towards the centre of the circle, and this force is responsible for keeping the object in circular motion.
This force is called centripetal force, and its magnitude is given by:
where
m is the mass of the object
is the angular velocity
r is the radius of the circle
For the ball in this problem we have:
m = 40 g = 0.04 kg is the mass of the ball
is the angular velocity
r = 30 cm = 0.30 m is the radius of the circle
Substituting, we find the force:
