Answer:
1). 
2). Toward us
3). 
4). Toward us
5). 
6). Away from us
7). 
8). Away from us
Explanation:
Spectral lines will be shifted to the blue part of the spectrum if the source of the observed light is moving toward the observer, or to the red part of the spectrum when it is moving away from the observer (that is known as the Doppler effect).
The wavelength at rest is 121.6 nm (
)

Then, for this particular case it is gotten:
Star 1: 
Star 2:
Star 3:
Star 4:
Star 1:
Toward us
Star 2:
Toward us
Star 3:

Away from us
Star 4:

Away from us
Due to that shift the velocity of the star can be determine by means of Doppler velocity.
(1)
Where
is the wavelength shift,
is the wavelength at rest, v is the velocity of the source and c is the speed of light.
(2)
<em>Case for star 1
:</em>
<em></em>
Notice that the negative velocity means that is approaching to the observer.
<em>Case for star 2
:</em>
<em>Case for star 3
:</em>
<em>Case for star 4
:</em>
In the given graph, from 4.0 s to 8.0 s, the object is at rest because the speed is zero.
In the given graph we can deduce the following;
- at the time interval, 0 s to 3.5 s, the speed of the object = 1 cm/s
- when the time, t= 4 s, the <em>speed</em> of the object = 0 cm/s
- at the time interval, 4.0 s to 8.0 s, the<em> speed </em>of the object = 0 cm/s
When the <em>speed</em> of an object is zero (0), the object is simply at rest.
Thus, we can conclude that in the given graph, from 4.0 s to 8.0 s, the object is at rest because the speed is zero.
Learn more here:brainly.com/question/10454047
Answer:
Approximately
(rounded down,) assuming that
.
The number of repetitions would increase if efficiency increases.
Explanation:
Ensure that all quantities involved are in standard units:
Energy from the cookie (should be in joules,
):
.
Height of the weight (should be in meters,
):
.
Energy required to lift the weight by
without acceleration:
.
At an efficiency of
, the actual amount of energy required to raise this weight to that height would be:
.
Divide
by
to find the number of times this weight could be lifted up within that energy budget:
.
Increasing the efficiency (the denominator) would reduce the amount of energy input required to achieve the same amount of useful work. Thus, the same energy budget would allow this weight to be lifted up for more times.