To determine the speed relative to the ground, since the ground is our reference frame, it would be v = 0, for the kid on the skateboard, you would need to take into account the speed that he/she is going and the speed of the keys thrown at.
I believe.
The density of the two pieces of rock is determined from the ratio of their masses to the pore volume of the rock.
<h3>What is density?</h3>
The density of an object is the ratio of mass to volume of the object.
Density = mass/volume
Assuming a constant pore volume of the rock = V
Density for 26.3 g = 26.3/V
Density for 58.3 g = 58.3g/V
Thus, the density of the two pieces of rock is determined from the ratio of their masses to the pore volume of the rock.
Learn more about density here: brainly.com/question/6838128
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The speed of waves are determined by the frequency of the push(wind). This really determines what the wave is being pushed by. If it were a Tsunami it would be by the frequency of the Tsunami if it were from the wind then the winds frequency would determine it's speed. Also the wavelength determines the speed because of the wight it has, but again something has to cause this wave to move.