Impulse

Definition

Impulse ($J$) is the product of the average force applied to an object and the time interval over which it acts, representing the change in momentum: $J = F\Delta t = \Delta p$.

Why It Matters

It governs vehicle safety design (e.g. crumple zones, airbags increase time to decrease peak force).

Core Concepts

• Momentum ($p$):
• How to read: “The momentum p is equal to the mass m times the velocity v.”
• Impulse ($I$):
• $I = Ft$ (Force $\times$ Time)
• How to read: “The impulse I is equal to the force F times the time interval t.”
• Meaning: Impulse is total force applied over a time interval.
• Impulse-Momentum Relationship: The impulse exerted on an object is equal to the change in momentum it produces.
• $Ft = \Delta(mv)$
• How to read: “The force times the time interval is equal to the change in momentum.”
• Meaning: Force over time changes momentum; this is the impulse-momentum theorem.
• Bouncing: Impulses are greater when an object bounces because the force must both stop the object and throw it back in the opposite direction.

Connected Concepts

• Momentum
• Inertia
• Conservation Laws (Physics)
• Newton’s Second Law of Motion