Select all that apply.
the spectrum of star y is compared to a reference hydrogen spectrum. what can be concluded about star y?
reference (normal)
hydrogen spectrum
star y
story

400 450 500 550 600 650 700
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750
star y is showing radial motion
star y is moving toward the earth
star y is moving away from the earth
star y is showing transverse motion

If a rock is thrown upward on the planet mars with a velocity of 12 m/s, its height (in meters) after t seconds is given by h = 12t − 1.86t2. (a) find the velocity of the rock after two seconds. m/s (b) find the velocity of the rock when t = a. 12−3.72a m/s (c) when will the rock hit the surface? (round your answer to one decimal place.) t = s (d) with what velocity will the rock hit the surface? m/s

Which of the following is the main energy source for the sun? a. fission of hydrogen b. fusion of hydrogen c. fusion of helium d. fission of iron

In a particular chemical reaction, the energy of the reactants is 30 kj and the energy of the products is 5 kj. 
 the maximum energy of the system is 40 kj. sketch a potential energy diagram for this reaction. make sure to label the energy of the reactants, the energy of the products, the activation energy, and the enthalpy change for the reaction.