really need help with 8th grade science! its HARD!!!?

Question

#1) the gravitational force between two objects (mass1= 10 kg, mass2=6 kg) is measured when the objects are 10 centimeters apart. if the 10 kg is replaced with 20kg mass and the 6kg mass is replaced with 12kg mass, how does the new gravitational attraction compare to the first one measured?

#2)the gravitational force between two objects (mass1= 10 kg, mass2=6 kg) is measured when the objects are 10 centimeters apart. if the distance between then is increased to 40 centimeters, how does the new gravitational attraction compare to the first one measured?

#3)The gravitational force between two objects (mass1=1kg, mass2=2kg) is measured when the objects are 12 centimeters apart. if the 1kg mass is replaced with a 5kg mass, and the 2 kg mass is replaced with a 4 kg mass, and the distance between the objuects is reduced to 4 centimeters, how does the new gravitational attraction cmpare to the first one measured?

I already posted this one time... but the answers i got were WAY above my 8th grade answers needed. I kno the answer to #3 is 90 but i dont kno if it is increased or decreased and i also dont kno how to do the work to get that answer. HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

Answer 1

1) it would be 4 times larger
2)it would be 16 times smaller
3)it would be 90 times the original

The way to solve this is to know how the force is related to the masses and to the distance.

Force= (some number)*mass1*mass2 / distance^2
the random number in front can be ignored for these problems.

So for example, in #1, mass1 is multiplied by 2 and mass2 is multiplied by 2. so Force is multiplied a total of 2*2=4

#2, the distance is multiplied by 4, so distance squared=4^2=16. So the force is divided by 16.

#3 is basically a combination of the first 2 problems.

Answer 2

1) Let us tackle them in a simple way.

Force of attraction between two masses m1 and m2 is given by F = m1.m2/r^2 where m1 and m2 are their masses and r is the distance between their centres of gravity. In this case, we have F1 = 10.6/10^2 and then we have the second case where F2 = 20.12/10^2

We need to compare F2 with F1. F2/F1 = 240/60 = 4
The new force is 4 times the earlier force.

2. When the distance is changed from 10 cm to 40 cm, the denominator is 16 times bigger and so the force is 16 times smaller. You can check by substituting the values in the formula given above.

3. This is a combination of the first two questions. Let us use the formula:

F1 = 1.2/12^2 units F2 = 5.4/4^2

F2/F1 = (20/2) X (144/16) = 10 X 9 = 90 times

Observe that the masses are increased 10 times and the distance is reduced by 3 times leading to the force increasing by another 9 times and thus we get a factor of 90 times.

Answer 3

gravitational force is proportional to the product of the masses divided by the square of the distance.

#1. both masses are doubled, so the force is quadrupled.
#2. the distance is quadrupled, so the force is 1/16 of the original
#3 The masses increase fivefold and double, producing 10 times the force. Thern the distance is reduced to 1/3 of the original, so the force is multiplied by 9. combining both effects makes the new force 90 times the old.