Answer:
40 j, 80j.
Explanation:
P.E= mgh. G=10 m/s².
For 4m, P.E=1*10*4=40 joules.
For 8m, P.E=1*10*8=80 joules.
Answer:
We need about 8769 meters of wire to produce a 2.6 kilogauss magnetic field.
Explanation:
Recall the formula for the magnetic field produced by a solenoid of length L. N turns, and running a current I:

So, in our case, where B = 2.6 KG = 0.26 Tesla; I is 3 amperes, and L = 0.57 m, we can find what is the number of turns needed;

Therefore we need about 39312 turns of wire. Considering that each turn must have a length of
, where D is the diameter of the plastic cylindrical tube, then the total length of the wire must be:

We can round it to about 8769 meters.
20/40=0.5 g/cm^3 becuase, mass/volume=density.
The answer is C hope this helps <span />