The density of the nugget is 
and is made of gold
Explanation:
The density of an object can be calculated as
where
d is the density
m is the mass
V is the volume of the object
We have to note that density of an object actually depends on the material the object is made of (therefore, two objects made of the same material can have different mass and different volume, but they have same density).
For the nugget in this problem, we have:
mass: m = 38 g
volume: 
So, its density is
And by looking at the table, we see that this value corresponds approximately to the density of gold, so the nugget is made of gold.
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A direct-current (DC) generator is a rotating machine that supplies an electrical output with unidirectional voltage and current. ... The field is produced by direct current in field coils or by permanent magnets on the stator. The output, or armature, windings are placed in slots in the cylindrical iron rotor.
Answer:
240m/s
Explanation:
The equation to calculate is wavelength= velocity/ frequency so to find the velocity you would have to multiply frequency by wavelength.
a) 2.75 s
The vertical position of the ball at time t is given by the equation
where
h = 4 m is the initial height of the ball
u = 12 m/s is the initial velocity of the ball (upward)
g = 9.8 m/s^2 is the acceleration of gravity (downward)
We can find the time t at which the ball reaches the ground by substituting y=0 into the equation:
This is a second-order equation. By solving it for t, we find:
t = -0.30 s
t = 2.75 s
The first solution is negative, so we discard it; the second solution, t = 2.75 s, is the one we are looking for.
b) -15.0 m/s (downward)
The final velocity of the ball can be calculated by using the equation:
where
u = 12 m/s is the initial (upward) velocity
g = 9.8 m/s^2 is the acceleration of gravity (downward)
t is the time
By subsisuting t = 2.75 s, we find the velocity of the ball as it reaches the ground:
And the negative sign means the direction is downward.
