Question

Two pickup trucks each have a mass of 2,000 kg. The gravitational force between the trucks is 3.00 × 10-5 N. One pickup truck is then loaded with 1,000 kg of bricks. Which of the following would be the new gravitational force between the two trucks?

Answer 1

Answer:

New gravitational force would be: $4.5\,\,\,10^{-5}\,\,\,N$

Explanation:

Recall the general form of the gravitational force between two objects of masses m1 and m2 separated a distance "d":

$F_g=G\,\frac{m1\,*\, m2}{d^2}$

which for the 2000 kg trucks becomes:

$F_g=G\,\frac{m1\,*\, m2}{d^2} \\3\,\,\,10^{-5}\,N=G\,\frac{2000\,*\, 2000}{d^2}$

when we add 1000 kg of bricks to one truck, we get the following unknown force (x) that we need to find:

$F_g=G\,\frac{m1\,*\, m2}{d^2} \\x=G\,\frac{3000\,*\, 2000}{d^2}$

Now we divide term by term the last equation by the previous one, in order to cancel out common factors to both equation (G, d^2) and get the following equation:

$\frac{x}{3\,\,\,10^{-5}} =\frac{3000}{2000} \\x=\frac{9}{2} \,10^{-5} =4.5\,\,\,10^{-5}\,\,\,N$