<span>They are used to measure and map effluent and pollution discharges from factories and sewerage plants, and the movement of sand around harbours, rivers and bays. Radioactive materials used for such purposes have short half-lives and decay to background levels within days.</span>
Gravitational force is given by, 
Where, m and M are the masses of the objects, R is the distance between them and G gravitational constant.
Gravitational force of the star on planet 1, 
Gravitational force of the star on planet 2, 
Ratio, 

Therefore, the gravitational force of the star on the planet 1 is three times that on planet 2.
Um you should putting it in a object that it can fill then go from there
Answer:

Explanation:
The density changes means that the length in the direction of the motion is changed.
Therefore,

Given :
Side, b = h = 0.13 m
Mass, m = 3.3 kg
Density = 8100 
So,


l = 0.024 m
Then for relativistic length contraction,







Therefore, the speed of the observer relative to the cube is 0.9833 c (in the units of c).
Laurentia, also called the North American Craton, is a huge continental craton. It<span> forms the ancient </span>geological<span> core of the </span>continent of North America.<span> It is made up of present day North America and Greenland. About 300 million years ago, it collided with the southern hemispheric continent of </span>Gondwana<span> and formed the supercontinent called Pangaea.</span><span> </span>