Answer
The maximum possible speed without breaking a bone is 2.21 m/s.
Work Step by Step
We can find the maximum force that the skater can hit the area of the forehead.
$F = (1.03\times 10^8~N/m^2)(1.5\times 10^{-4}~m^2)$
$F = 1.55\times 10^4~N$
The impulse will be equal in magnitude to the change in momentum.
$mv = F~t$
$v = \frac{F~t}{m} = \frac{(1.55\times 10^4~N)(0.0100~s)}{70.0~kg}$
$v = 2.21~m/s$
The maximum possible speed without breaking a bone is 2.21 m/s.
