Your forehead can withstand a force of about 6.0 kN before fracturing, while you

Question

Your forehead can withstand a force of about 6.0 kN before fracturing, while your cheekbone can only withstand about 1.3 kN .

Part A -

If a 140 baseball strikes your head at 39 m/s and stops in 1.2 x 10^-3s , what is the magnitude of the ball's acceleration? Express your answer using two significant figures

Part B -

What is the magnitude of the force that stops the baseball? Express your answer using two significant figures

Part C -

What force does the baseball apply to your head? Express your answer using two significant figures

Part D -

Are you in danger of a fracture if the ball hits you in the forehead? Yes/No

Paet E-

Are you in danger of a fracture if the ball hits you in the cheek? Yes/No

Explanation / Answer

a) a = change in speed/change in time = (0 - 39 m/s)/1.2*10?3 s = 3.25*10^4 m/s^2

b) force F = ma = (0.14 kg) (3.25 x 10^4 m/s^2) = 4550 N or 4.55 kN

c) Equal and opposite to (b), i.e. 4.55 kN

d) 4.55 kN < 6 kN. No.

e) 4.55 kN > 1.3 kN. Yes.

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