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Physics For Scientists & Engineers
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Short Answer

(a) Estimate the force with which a karate master strikes a board, assuming the hand's speed at the moment of impact is 10.0 m / s} and decreases to 1.00 m /s during a 0.00200-s time interval of contact between the hand and the board. The mass of his hand and arm is 1.00Kg.

(b) Estimate the shear stress, assuming this force is exerted on a 1.00cm -thick pine board that is 10.0 cm wide.

(c) If the maximum shear stress a pine board can support before breaking is 3.60×106 N/m2, will the board break? Determine the convergence set of the given power series.

a) F=4500 Nb) S=4.5×106Nm2

c) We can see that karate master applies greater shear stress than board can handle, so it will break.

See the step by step solution

Step by Step Solution

Step 1: We are given following data for a karate master striking a board:

(a)

Δt=0.002 sm=1 mv1=10msv2=1  ms

Calculating the force that karate master use to strike a board:

F&=m×a=m×ΔvΔt=m×v1-v2Δt=1×10-10.002=4500 N

Step 2:  Board dimensions are given by

(b)

t=0.01 m2=0.1 m

Board surface area is equal to:

A=t×w=0.01×0.1=0.001 m2

Calculating shear stress

S=FA=45000.001=4.5×106Nm2

Step 3: Maximum shear stress a pine board can support is equal to

(c)

S=3.6×106Nm2

We can see that karate master applies greater shear stress than board can handle, so it will break.

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