Answer:

Explanation:
Hello,
In this case, considering that the acceleration is computed as follows:

Whereas the final velocity is 28.82 m/s, the initial one is 0 m/s and the time is 4.2 s. Thus, the acceleration turns out:

Regards.
Answer:
77J
Explanation:
Not really an explanation to this, I just had this lesson last year and remembered it.
Hope I helped! ☺
Answer:0.6kw
Explanation:
Power=force×velocity
Power=20×30=600w
In kw it's going to be 600/1000=0.6kw
Answer:
the moment of inertia with the arms extended is Io and when the arms are lowered the moment
I₀/I > 1 ⇒ w > w₀
Explanation:
The angular momentum is conserved if the external torques in the system are zero, this is achieved because the friction with the ice is very small,
L₀ = L_f
I₀ w₀ = I w
w =
w₀
where we see that the angular velocity changes according to the relation of the angular moments, if we approximate the body as a cylinder with two point charges, weight of the arms
I₀ = I_cylinder + 2 m r²
where r is the distance from the center of mass of the arms to the axis of rotation, the moment of inertia of the cylinder does not change, therefore changing the distance of the arms changes the moment of inertia.
If we say that the moment of inertia with the arms extended is Io and when the arms are lowered the moment will be
I <I₀
I₀/I > 1 ⇒ w > w₀
therefore the angular velocity (rotations) must increase
in this way the skater can adjust his spin speed to the musician.
if in series one lightbulb burns out the rest are unable to turn on.
In parallel a single light bulb burns out any other light bulbs are able to work.
Parallel is the best to use during holidays.