Which instrument uses three beams to measure mass accurately?

• A. Triple Beam Balance
• B. Barometer
• C. Weather Vane
• D. Telescope

Answer: (A)

This question tests how mass is measured precisely with a mechanical balance that uses multiple sliding weights. A triple beam balance carries three beams, each with a rider that slides to a specific value. One beam tracks hundreds of grams, another tens, and the smallest ones. You place the object on the pan, slide the riders until the balance pointer is at zero, and then add up the readings from all three beams to get the object’s mass in grams. This setup lets you read fine increments quickly and accurately, which is why it’s designed with three beams to measure mass.

The other instruments measure different things: a barometer gauges atmospheric pressure, a weather vane shows the wind’s direction, and a telescope helps view distant objects. None of these use three beams to determine mass.