Weight

Weight is the force with which the Earth attracts a body towards itself.
It depends on the mass of the object and the acceleration due to gravity (g).
Unlike mass, weight is not constant and changes with the value of g.

Definition and Formula

Weight (W) = mass (m) × gravitational acceleration (g)
Formula: W = m × g
Unit: Newton (N)
On Earth, g = 9.8 m/s²
Weight acts downward, toward the center of the Earth

📝 PYQ (BPSC): Weight of a body is measured in? → Newton
📝 Expected MCQ: What is the value of g on Earth? → 9.8 m/s²

Mass vs Weight

Property	Mass	Weight
Definition	Amount of matter	Force due to gravity
SI Unit	Kilogram (kg)	Newton (N)
Changes?	Constant everywhere	Changes with gravity
Measured by	Beam balance	Spring balance

📝 Expected MCQ: Instrument used to measure weight? → Spring balance

Variability of Weight

Weight is maximum at poles, minimum at equator (due to Earth’s shape)
Weight is zero in space (free fall or orbit) → Astronauts feel weightless
On Moon: g = 1/6 of Earth → weight = 1/6th of Earth weight

📝 PYQ (BPSC Teacher): Why do astronauts feel weightless? → Zero gravity or free fall
📝 Expected MCQ: Weight of a 60 kg person on Moon? → ~10 N

Effects of Weight in Daily Life

Determines load capacity in machines, vehicles
Affects building design, bridges, dams
Plays a role in seed packaging, fertilizer weighing (Bihar agriculture)
Disaster management: Earthquake-resistant buildings consider weight distribution
In sports: weight categories in wrestling, boxing, etc.

Bihar Context

Agricultural produce (e.g. grains, vegetables) is traded by weight
Government PDS shops use electronic balances for fair distribution
Awareness programs against weighing frauds in rural markets
Flood management involves weighing sandbags, relief materials
Bihar School Olympics include weight-based sports categories

PYQs + Expected MCQs

📝 PYQ (BPSC): Unit of weight? → Newton
📝 PYQ (BPSC Teacher): Why is weightless condition observed in space? → No gravity
📝 Expected MCQ: What affects weight but not mass? → Gravitational force
📝 Expected MCQ: On Moon, weight becomes? → 1/6 of Earth weight
📝 Expected MCQ: Weight is measured using? → Spring balance
📝 Expected MCQ: At which point is Earth’s gravity maximum? → Poles

Quick Revision Points

Weight = m × g
SI Unit = Newton
Mass is constant, weight changes with g
Measured using spring balance
On Moon → weight = 1/6 × Earth weight
Zero weight in free fall or orbit
Bihar use: agri-trade, PDS, sandbag weighing in floods

Sources Used

NCERT Science Class 6–9
Lucent GK – Physics Section
Drishti Science Quick Book
EduTeria + Ghatna Chakra BPSC PYQs
Bihar Agri Marketing Reports & PDS Guidelines
Bihar Disaster Management Authority Notes