1. What is the gravitational force between two point masses m1 and m2 separated by distance r?
A.
Gm1m2/r
B.
Gm1m2/r^2
C.
Gm1m2r^2
D.
G(m1+m2)/r^2
Correct Answer:
Gm1m2/r^2
Explanation:
According to Newton's law of universal gravitation, the force between two point masses is F = Gm1m2/r^2.
2. If the distance between two point masses is doubled, their gravitational force becomes:
A.
Twice the original force
B.
Half the original force
C.
One-fourth the original force
D.
Four times the original force
Correct Answer:
One-fourth the original force
Explanation:
Gravitational force is inversely proportional to the square of the separation, so doubling the distance makes the force one-fourth.
3. If one of two point masses is doubled while the distance between them remains unchanged, the gravitational force becomes:
A.
Half the original force
B.
Unchanged
C.
Twice the original force
D.
Four times the original force
Correct Answer:
Twice the original force
Explanation:
The gravitational force is directly proportional to each mass. Therefore, doubling one mass doubles the force.
4. The gravitational force between two point masses acts along the:
A.
Perpendicular bisector of the line joining them
B.
Line joining their centers
C.
Tangent to their circular paths
D.
Vertical direction only
Correct Answer:
Line joining their centers
Explanation:
For two point masses, the gravitational force acts along the straight line joining the two masses.
5. What is the SI unit of the gravitational constant G?
A.
N kg^2 m^-2
B.
N m kg^-2
C.
N m^2 kg^-2
D.
kg m^2 N^-2
Correct Answer:
N m^2 kg^-2
Explanation:
From F = Gm1m2/r^2, the SI unit of G is N m^2 kg^-2.
6. Two point masses attract each other with equal gravitational forces because of:
A.
Conservation of mass
B.
Newton's third law of motion
C.
The law of conservation of energy
D.
The law of inertia
Correct Answer:
Newton's third law of motion
Explanation:
The two masses exert equal-magnitude gravitational forces in opposite directions on each other, as stated by Newton's third law.
7. If both masses in a two-point-mass system are doubled and their separation remains unchanged, the gravitational force becomes:
A.
Unchanged
B.
Twice the original force
C.
Four times the original force
D.
Eight times the original force
Correct Answer:
Four times the original force
Explanation:
Since F is proportional to m1m2, doubling both masses multiplies their product by four, so the force becomes four times larger.
8. The gravitational force between two point masses is always:
A.
Repulsive
B.
Attractive
C.
Zero
D.
Alternately attractive and repulsive
Correct Answer:
Attractive
Explanation:
Gravitational interaction between two positive masses is always attractive, pulling the masses toward each other.
9. If the separation between two point masses is reduced to half its original value, the gravitational force becomes:
A.
One-fourth the original force
B.
Half the original force
C.
Twice the original force
D.
Four times the original force
Correct Answer:
Four times the original force
Explanation:
Because force varies as 1/r^2, replacing r by r/2 increases the force by a factor of four.
10. Which expression gives the magnitude of the gravitational force between two point masses of 2 kg and 3 kg separated by distance r?
A.
6G/r
B.
5G/r^2
C.
6G/r^2
D.
G/(6r^2)
Correct Answer:
6G/r^2
Explanation:
Using F = Gm1m2/r^2 with m1 = 2 kg and m2 = 3 kg gives F = G(2)(3)/r^2 = 6G/r^2.
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