CLASSICAL MECHANICS & THERMODYNAMICS - Chapter 10 (Capstone), Exercise 1 Solution ========================================================== A Redesigned Piston: Force, Acceleration, and Launch Speed PROBLEM ------- A redesigned piston has area A = 0.06 m^2 and the same steam pressure, P = 200,000 Pa, over the same 3 m stroke, launching a lighter 350 kg car. Find the new launch force, acceleration, and launch speed. SOLUTION -------- Step 1: Find the new launch force. F = P A F = 200,000 x 0.06 F = 12,000 N Step 2: Find the new acceleration (Chapter 2, F = ma). a = F / m a = 12,000 / 350 a = 34.29 m/s^2 (approximately) Step 3: Find the launch speed (Chapter 1, v^2 = u^2 + 2as, u = 0). v^2 = 2 a d v^2 = 2 x 34.29 x 3 v^2 = 205.7 v = sqrt(205.7) v = 14.34 m/s (approximately) ANSWER: The new launch force is 12,000 N, the acceleration is approximately 34.29 m/s^2, and the launch speed is approximately 14.34 m/s. ---- WHY THIS WORKS AS AN ANSWER A larger piston area (0.06 m^2 vs. the capstone's original 0.05 m^2) increases the launch force even at the same steam pressure, since force scales directly with area (F = PA). Combined with a LIGHTER car (350 kg vs. 400 kg), the resulting acceleration increases even more sharply, since acceleration depends on both a larger force AND a smaller mass (a = F/m) - both changes push acceleration, and therefore launch speed, higher than the capstone's own original 12.25 m/s result. This exercise mirrors the exact same three-step chain used in the capstone itself (Step 4: force, then acceleration; Step 5: launch speed), just with different design parameters.