Momentum: Question 6

Worked solution

Step 1: Recall the definition of momentum

Linear momentum is defined as mass times velocity: $p = mv$

Momentum is a vector, so its full description includes a direction, but here we are only asked for the magnitude.

Step 2: Substitute the given values

The drone has mass $m=4\text{ kg}$ and speed $v=12\text{ m s}^{-1}$: $p = mv = 4 \times 12 = 48\text{ kg m s}^{-1}$

Why the other options are wrong

• B ($16\text{ kg m s}^{-1}$): this comes from adding the mass and velocity, $4+12=16$, instead of multiplying them.
• C ($3\text{ kg m s}^{-1}$): this comes from dividing velocity by mass, $12\div4=3$, instead of multiplying.
• D ($96\text{ kg m s}^{-1}$): this is double the correct value, e.g. from mistakenly multiplying by $2m$ or $2v$.

Final answer

• Magnitude of momentum $= \boxed{48}\text{ kg m s}^{-1}$, option A.