Estimate the force with which a karate master strikes a board if the hand's speed at time of impact is 4.78m/s, decreasing to 1.55m/s during a constant time of 0.00239 s with the board. The mass of coordinated hand and arm is 0.701 kg. Answer in units of N.

Question

Estimate the force with which a karate master strikes a board if the hand's speed at time of impact is 4.78m/s, decreasing to 1.55m/s during a constant time of 0.00239 s with the board. The mass of coordinated hand and arm is 0.701 kg. Answer in units of N.
Estimate the shear stress if this force is exerted on a 1.31 cm thick pine board that is 6.35 cm wide. Answer in units of N/m^2

Ashleigh · Answer

I figured this question out: F = (mass of the arm x change in velocity)/time So, ((0.701kg.)(4.78m/s-1.55m/s))/(0.00239s) = 947.376569 And shear stress is F/Area = (947.376569N)/((0.0635m)(0.0131m))