text: question-stress/strain/modulus? i'm stuck--can anyone help? thanks in advance.   the total cross-sectional area of the load-bearing calcified portion of the two forearm bones (radius and ulna) is approximately 2.2 cm^2. during a car crash, the forearm is slammed against the dashboard. the arm comes to reast from an initial speed of 80 km/hr in .0047 sec. if the arm has an effective mass of 3.0 kg, what is the compressional stress that the arm withstands during the crash? assume the forearm is pointed straight forward, so the force is directed along its long axis. calculate the force on the arm from f=ma, with m 3.0kg, and a the acceleration 80kph/.0047sec (fix the units so it's all m/sec first). then you have the force, and you have the cross-sectional area that's bearing that load, so f/a=p to get the pressure or stress. maybe divide by two if there's two bones.