An object weighs 10 N on the earth's surface. What is the weight of the object on a planet that has one tenth the earth's mass and one half the earth's radius?
A)4 N
B)2 N
C)1 N
D)10 N
E)20 N

Question

Quizplus · Accepted Answer

The gravitational force (weight) is proportional to the mass of the planet and inversely proportional to the square of its radius. If the planet has one tenth the Earth's mass and one half the Earth's radius, the weight is (1/10) / (1/2)^2 = 4 times less than on Earth, so 10 N / 4 = 2.5 N, but since the calculation was incorrect, the correct answer is 4 N.

An Object Weighs 10 N on the Earth's Surface