Unit: Mechanics
Year: 1989 Question#: 14
Question: Gravitational force of attraction F exists between two masses A and B when they are separated by a fixed distance. After mass A is tripled and mass B is halved, the gravitational attraction between the two masses is:
(1 ) 1/6 F
(2 ) 2/3 F
(3 ) 3/2 F
(4 ) 6 F
What is this question really asking?
Explanation by: JD W.
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Answer 1
1/6 F
INCORRECT
Mass A has been tripled. So the force from A to B is increased 3 times. Mass B has been decreased by a half, so that increases the force between mass A and B by 1/2 so the force would not be1/6 F return to top
Answer 2
2/3 F
INCORRECT
Mass A has been tripled. So the force from A to B is increased 3 times. Mass B has been decreased by a half, so that increases the force between mass A and B by 1/2 so therefore the answer is not 2/3 F. return to top
Answer 3
3/2 F
CORRECT
Nice use of the formula
. Mass A has been tripled. So the force from A to B is increased 3 times. Mass B has
been decreased by a half, so that increases the force between mass A and B by 1/2
Combining the tripling and the halving you would get half of 3 which would look like
(3/2) F return to top
Answer 4
6 F
INCORRECT
Mass A has been tripled. So the force from A to B is increased 3 times. Mass B has been decreased by a half, so that increases the force between mass A and B by 1/2 so the answer could not be 6 F. return to top
What's this question really asking?
This question is basically asking about gravitational force. If the initial force was equal, then mass A was tripled and mass B was decreased by half, what's the force of attraction now?
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