20/40=0.5 g/cm^3 becuase, mass/volume=density.
Answer:

Explanation:
Average velocity is defined as the ratio of total displacement of the motion and total time taken in that motion
here we know that initially the sky diver drops without opening parachute by total displacement 625 m
then she open her parachute and drop another 362 m
so first it took time t = 15 s to drop without open parachute
then it took t = 139 s to drop next displacement
so here total displacement is given as

total time is given as

so average velocity is given as


Answer: 10.3m/s
Explanation:
In theory and for a constant velocity the physics expression states that:
Eq(1): distance = velocity times time <=> d = v*t for v=constant.
If we solve Eq (1) for the velocity (v) we obtain:
Eq(2): velocity = distance divided by time <=> v = d/t
Substituting the known values for t=15s and d=155m we get:
v = 155 / 15 <=> v = 10.3
Correct answer is:
<h2>The maximum number of orbits in an atom is <u>Seven.</u></h2><h3>Explanation:</h3>
Every energy level has a limited one orbital including two electrons. The orbits are settled in the sub-levels and there can be further than 1 sub-level as the number of energy levels rises. On energy level 1, there is 1 sub-level and 1 orbital. Energy level 2 can possess 2 sub-levels and 2 orbitals. These remain to develop as you progress from the nucleus of the atom, closing up with an infinite potential number of levels and orbits.