Been on holiday for a while…

Impulse

Impulse is the change in momentum caused by force over time.

(J = FΔt)

Or

Impulse = Force x time interval = mass x change in velocity

Application:

Extending contact time (Δt) reduces impact force (e.g., rolling with a punch).

Short, sharp strikes (small Δt) maximise force.

Rotational Mechanics : Torque & Angular Momentum

Torque

(τ = r × F)

Rotational Torque depends on the distance (r) from the pivot point and the force (F).

Application:

– Spinning kicks generate more power due to rotational force.

– Joint locks (e.g., armbars) apply torque to limbs.

Angular Momentum

Depends on rotational inertia (I) and angular velocity (ω).

L = Iω

Application:

Contracting the body (reducing I) increases speed (ω) for spinning kicks.

Consider an attacker approaching a defender. The defender can side step the attacker as they grab the attacker’s arm, assisting the attacker in continuing in the direction of his motion momentarily. Blending their masses together, the defender can convert the linear momentum of the attacker into angular momentum of rotation. Decreasing the radius of rotation of the attacker will increase his speed.

If the defender now stops their own rotation, conservation of angular momentum says that the attacker will gain almost all of the momentum of the combined system of bodies. This will cause the attacker to ‘leave his feet behind’ and potentially fall to the ground.

In Kyushindo this is why emphasis is made on being at the centre of a circle when performing various techniques. You are the centre and the opponent is on the edge. This translates into a small movement from you giving a larger movement in the opponent – a more efficient way (less effort on your part).

Bagua uses contraction then expansion of the body and limbs, again at the centre of a circle, in performing techniques.