Grade 4 (age 9-10)

grade 4 Weight Measurement

Weight Measurement

Weight is how heavy an object is, and a pan balance measures it against small weights. Put the object on one pan and the small weights on the other; when the pans sit level, those weights add up to the object's weight. Weight comes from gravity, so on the Moon it drops to a sixth of Earth's while mass stays the same everywhere. Move the sliders for the object and the weights and the balance tips or sits level.

Let's measure weight

Object weight50g

Weight piece30g

⚖️ Using a pan balance

①Place the object on the left pan

②Place weights on the right pan

③Adjust weights until level

④Sum of weights = the object's weight!

Weight and Mass

🌍 Weight vs. Mass

①Mass: amount of matter — same everywhere

②Weight: gravitational pull — varies by place

③On the Moon, weight is 1/6 of Earth's

④But mass is the same on Earth and Moon

⑤A pan balance compares both sides, so it still levels with the same weights on the Moon. Feeling lighter happens when you measure force, as with a spring scale

Summary

Weight Measurement

When level: object weight = sum of weights

A pan balance gives precise weight

Weight Units

g (gram), kg (kilogram) — 1 kg = 1000 g

Common everyday units

Weight vs Mass

Weight (force) ≠ Mass (amount of matter)

Weight changes by place; mass is constant

🎯 Key Points

①Pan balance measures weight using weights

②Level means equal weight

③Units: g, kg

④Weight is the force from gravity

⑤Mass never changes by location

Examples and Unit Test

Example 1

On a pan balance, an object on one side balances the weights on the other. If the weights are 30 g and 20 g, what is the weight of the object?

When a pan balance is level, the weights on both sides are equal.

The weight of the object equals the sum of the weights placed, so 30 g + 20 g = 50 g.

▸ 50 g

When the balance is level, the weight of the object equals the sum of the weights.

Example 2

A person with a mass of 60 kg goes to the Moon. What happens to their weight and mass? (Moon gravity is 1/6 of Earth.)

Mass is the amount of matter in an object, so it does not change with location.

Weight is the pull of gravity, so on the Moon, where gravity is 1/6, the weight becomes 1/6 of that on Earth.

▸ Mass = 60 kg (unchanged) / weight = reduced to 1/6 of Earth

Mass is the same everywhere; weight differs by location depending on gravity.

Unit-test style

Which statement about weight and mass is correct?

①Mass changes when the location changes

②Weight is the pull of gravity

③On the Moon the mass of an object is reduced to 1/6

④If a pan balance is level, the object is heavier than the weights

⑤Weight and mass mean exactly the same thing

▸ ② Weight is the pull of gravity

Weight is the force of gravity pulling on an object, so where gravity differs, the weight differs too.

Mass is the same everywhere (① and ③), a level balance means equal weights on both sides (④), and weight is a force while mass is the amount of matter, so they differ (⑤).

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