Question 1
A student says, 'My weight is 45 kg.' What is wrong with this statement?No clue? Show me the answer
Correct answerCorrect!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Identify the two quantities: mass and weight
Mass is the amount of matter in an object, measured in kilograms (kg). Weight is the gravitational force acting on an object, measured in newtons (N).
Step 2: Apply the definitions to the statement
The student says their weight is 45 kg. Since weight is a force, it must be expressed in newtons (N), not kilograms. Saying '45 kg' describes mass, not weight.
Step 3: Select the correct answer
The error is that weight should be measured in newtons, not kilograms. The student is confusing weight (a force) with mass (amount of matter).
Method #2Process of EliminationStep 1: Identify what is being asked
We need to find what is scientifically incorrect about describing weight in kilograms.
Step 2: Eliminate 'metres per second'
The option saying weight should be in metres per second is wrong — metres per second is a unit of speed, not force or weight.
Step 3: Eliminate 'nothing is wrong'
'Nothing is wrong — weight and mass are the same thing' is incorrect because in science, weight and mass are very different quantities with different units.
Step 4: Eliminate 'grams instead of kilograms'
Suggesting grams instead of kilograms is still the wrong unit entirely — weight is a force and must be in newtons regardless of the size.
Step 5: Select the correct answer
The correct answer is that weight should be measured in newtons, not kilograms. Kilograms measure mass, while newtons measure the gravitational force (weight).
Question 2
An astronaut has a mass of 80 kg on Earth. They travel to Mars where . Which statement is correct?No clue? Show me the answer
Correct answerCorrect!IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Recall the difference between mass and weight
Mass does not change with location — it is always the same number of kilograms. Weight changes because it depends on the local gravitational field strength .
Step 2: Confirm mass stays the same
The astronaut's mass remains 80 kg on Mars, just as it is on Earth.
Step 3: Calculate the new weight on Mars
Step 4: Select the correct answer
The astronaut's mass is still 80 kg and their weight on Mars is 296 N — much less than on Earth because Mars has a weaker gravitational field.
Method #2Process of EliminationStep 1: Identify what changes and what doesn't
The key principle is that mass is constant anywhere in the universe, while weight depends on .
Step 2: Eliminate 'mass decreases to 296 kg'
Mass never changes based on location — saying mass becomes 296 kg on Mars confuses mass with weight and is incorrect.
Step 3: Eliminate 'weight increases because Mars is farther from the Sun'
Weight depends on the planet's own gravitational field strength, not on distance from the Sun. Mars has lower than Earth, so weight decreases, not increases.
Step 4: Eliminate 'both mass and weight are 80 kg'
Weight is measured in newtons, not kilograms. Also, weight changes on Mars. This option is doubly incorrect.
Step 5: Select the correct answer
The correct answer is that mass stays at 80 kg and weight becomes on Mars.
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