Final answer:
The gravitational force acting on a mass 2m placed at the centroid G of an equilateral triangle with three equal masses of m kg fixed at the vertices can be calculated using the equation F = G * (m1 * m2) / r^2. By considering the forces from the other three masses, we can determine the force in both scenarios by plugging in the appropriate values and performing the necessary calculations.
Step-by-step explanation:
a) To find the gravitational force acting on a mass 2m placed at the centroid G, we need to consider the forces acting on it from the three masses at the vertices of the equilateral triangle ABC.
Since the masses are fixed, the only force acting on the mass 2m will be due to the gravitational pull from the other three masses.
The gravitational force between two objects is given by the equation F = G * (m1 * m2) / r^2, where G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between their centers of mass.
Using this equation, we can calculate the force acting on the mass 2m at the centroid G.
b) If the mass at vertex A is doubled, the force acting on the mass 2m at the centroid G will also change.
We can use the same equation to calculate this force by considering the new mass at vertex A.
By plugging in the appropriate values into the equation and performing the necessary calculations, we can determine the force acting on the mass 2m in both scenarios.