Charpy impact test pendulums are used to determine the amount of energy a test specimen absorbs during an impact (see astm standard e23). the hammer weighs 71.2 lbs and has a mass moment of inertia about its center of gravity gh of 20.9 slug·in2 . the arm weighs 19.5 lbs and has a mass moment of inertia about its own center of gravity ga of 47.1 slug·in2 . the pendulum is released from rest from an initial position of θ = 39°. knowing that the friction at pin o is negligible, determine (a) the impact speed when the hammer hits the test specimen, (b) the force on the pin o just before the hammer hits the test specimen, (c) the amount of energy that the test specimen absorbs if the hammer swings up to a maximum of ϕ = 70° after the impact