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## Main Question or Discussion Point

When you punch someone in the face and leave your hand there, it'll be less effective than doing a strike where contact time is kept minimal: hit and back.

The reason is the conservation of linear momentum and impulse.

In the first case:

(As the force-average is the change in the momentum of system(hand+face) divided by

Δt)

F=(Pfinal - Pinitial)/Δt=(0-Pinitial)/Δt=-Pinitial/Δt

[P hereby refers to the initial and final momentum of hand and therefore minus sign becomes + when subtraction is carried out as the direction of the speed changes]

In the second case:

F=(Pfinal - Pinitial)/Δt

so anything added to the Pfinal will increase the Force applied to face by also keeping the time minimal.

Am I correct?

The reason is the conservation of linear momentum and impulse.

In the first case:

(As the force-average is the change in the momentum of system(hand+face) divided by

Δt)

F=(Pfinal - Pinitial)/Δt=(0-Pinitial)/Δt=-Pinitial/Δt

[P hereby refers to the initial and final momentum of hand and therefore minus sign becomes + when subtraction is carried out as the direction of the speed changes]

In the second case:

F=(Pfinal - Pinitial)/Δt

so anything added to the Pfinal will increase the Force applied to face by also keeping the time minimal.

Am I correct?