An object placed on an equal-arm balance requires 12 kg to balance it.When placed on a spring scale, the scale reads 12 kg.Everything (balance, scale, set of weights and object)is now transported to the Moon where free-fall acceleration is one-sixth that on Earth.The new readings of the balance and spring scale (respectively)are:
A)12 kg, 12 kg
B)2 kg, 2 kg
C)12 kg, 2 kg
D)2 kg, 12 kg
E)12 kg, 72 kg

Question

Quizplus · Accepted Answer

On the Moon, the weight of the object changes due to the difference in free-fall acceleration. The weight on the moon would be 1/6 of its weight on Earth. Therefore, the weight of the object on the Moon would be:

W = 1/6 * 12 kg = 2 kg

However, the mass of the object remains the same, and so does the reading on the spring scale. Therefore, the spring scale would still read 12 kg, even though the weight of the object has changed.

On the balance scale, the weights used to balance the object have not changed in mass, and so their weight would also reduce by a factor of 1/6 on the Moon. Therefore, to balance the object, the balance would require:

12 kg * (1/6) = 2 kg

The mass of the object is still the same, and so it would require the same mass of weights to balance it. Therefore, the new readings on the balance scale and the spring scale would be 2 kg and 12 kg, respectively.

Hence, the correct choice is C.

An Object Placed on an Equal-Arm Balance Requires 12 Kg