In introductory mechanics, impulse $J$ is defined as $J=F\Delta t$. What are the SI units of impulse?

• A. $N\cdot s$
• B. $W$ (watt)
• C. $N\cdot m$
• D. $J$ (joule)

Answer: (A)

Verified step by step guidance

1. Recall the definition of impulse: \(J = F \Delta t\), where \(F\) is force and \(\Delta t\) is the time interval over which the force acts.
2. Identify the SI unit of force \(F\), which is the newton (N). One newton is defined as \$1\ \mathrm{N} = 1\ \mathrm{kg} \cdot \mathrm{m/s^2}$.
3. Identify the SI unit of time \(\Delta t\), which is the second (s).
4. Combine the units of force and time to find the unit of impulse: \(\mathrm{N} \cdot \mathrm{s}\).
5. Understand that \(\mathrm{N} \cdot \mathrm{s}\) is the correct SI unit for impulse, distinguishing it from other units like watt (W), newton-meter (N·m), or joule (J).