Question

Two types of balances, beam balance and spring balance are commonly used for measuring weights in shops. If we are on the moon we can continue to use:

Answer 1

Hint-The spring balance measures the weight where as a beam balance measures the mass. We know that the acceleration due to gravity on earth and moon is different. So, the weight of the body on Earth and Moon will be different. Mass does not depend upon acceleration due to gravity. So, mass will remain constant even on the Moon.

Complete step by step solution:
Both beam balance and spring balance are commonly used for measuring weights in shops. The beam balance actually measures the mass whereas the spring balance measures the weight.

We know that spring balance works on the principle of hooke's law.

The hook slowly states that the force needed to stretch a spring is proportional to the displacement of the spring from its mean position.
$F = - kx$
Where, F is the force, k is the spring constant and x is the displacement.

The force produced by a load is the weight. So, the displacement produced by the weight is used to find the weight of the object.

Spring balance provides a simple and cheap method of measuring weight. We can measure the weight by simply hanging the load at one end of the spring. Since gravitational force is pulling the body downwards the spring will stretch downwards and the reading against the scale on the spring balance can be measured. That is how we measure the weight in a spring balance.

But a beam balance is used to measure mass of an object. It measures the mass by comparing the mass of an object with a known mass.

The beam balance consists of a horizontal beam which is supported at its centre. We balance the object by placing known weights on the other end. Since, we are balancing both the object and the known mass the effect of gravity gets cancelled. Because gravity acts on both of them equally.

Hence what we are actually measuring is the mass.

If the beam balance and spring balance are taken to the moon. Since beam balance does not depend upon the gravity, we will get the same measurement of mass even if the gravitational force on the moon is different than that of earth.

But if we are measuring using spring balance the reading will be different. Because the weight of the object on the moon will be different from the weight on Earth. We know that weight is calculated as mass times the acceleration due to gravity.
$W = mg$
Where, m is the mass and g is the acceleration due to gravity.
So, the weight of the object as shown by the spring balance will be different.
Hence if we are on the moon, we can continue to use beam balance.

Note: Remember that mass and weight are different. Mass of an object is the amount of matter contained in it. It will not change if the acceleration due to gravity changes. But weight is a measure of force with which the earth pulls an object due to gravity. Weight on Earth and Moon will be different because the acceleration due to gravity is different on earth and moon.