Describing Forces - Weight, Tension, Friction

A bathroom scale measures the gravitational force acting on the person — this is their weight. Weight is measured in Newtons (N), which matches the 600 N reading.

Weight is the gravitational force acting on an object due to a nearby massive body. Using $W=m\times g$, weight is calculated in Newtons and depends on gravitational field strength.

Mass is measured in kilograms (kg), not Newtons. Since the scale reads 600 N, this cannot be mass.

The 600 N reading represents the weight of the student — the gravitational force Earth exerts on them. This is the correct answer.

We need to identify what a 600 N reading on a bathroom scale represents, distinguishing between weight, mass, normal force, and friction.

Mass is measured in kilograms (kg), not Newtons. A reading in N cannot represent mass, so this option is eliminated.

The scale measures the force on itself, but by Newton's Third Law this equals the weight of the student — it is the weight being measured, not simply described as a normal force the student exerts.

Friction acts along surfaces opposing motion. A person standing still on a scale is not experiencing friction as the relevant vertical force — friction is not what scales measure.

The remaining option — the student's weight due to Earth's gravitational pull — is correct. Weight is measured in Newtons and is the gravitational force acting on the student.

The astronaut's mass $m=80$ kg (this does not change between planets). The gravitational field strength on the Moon is $g=1.6$ N/kg.

Use the equation $W=m\times g$ to calculate weight on the Moon: $W=80\times 1.6=128\text{ N}$

The astronaut's weight on the Moon is 128 N. Note that their mass remains 80 kg — only weight changes with gravitational field strength.

We need to calculate the astronaut's weight on the Moon using $m=80$ kg and $g_{Moon}=1.6$ N/kg.

800 N would be the weight on Earth ($80\times 10=800$ N). The question asks about the Moon, where gravity is much weaker, so this is too large.

80 N would result from $80\times 1=80$ N, using $g=1$ N/kg, which is not the Moon's gravitational field strength.

50 N would come from $80÷1.6=50$ — this incorrectly divides instead of multiplying. The formula is $W=m\times g$, not $m÷g$.

128 N is correct: $W=80\times 1.6=128$ N. This is the astronaut's weight on the Moon.