🔍 Key Concepts

• combustion chamber location in relation to the piston(s) • difference between single-acting, double-acting, and engines with two pistons per cylinder • how piston movement can form a common compression space between crowns

💭 Think About

• Picture where the fuel-air mixture actually burns: is it above one piston, on both sides of one piston, or between two opposing pistons? • Which of these engine types uses two pistons moving toward each other in the same cylinder to compress the charge? • Ask yourself: does "single-acting" or "double-acting" describe the number of combustion spaces per piston stroke, or the number of pistons sharing one combustion chamber?

✅ Before You Answer

• Identify which choice refers specifically to two pistons in one cylinder facing each other • Confirm which terms (single-acting vs double-acting) describe whether pressure is applied to one or both sides of the same piston • Eliminate any option that only refers to piston orientation (vertical/horizontal) rather than the number and arrangement of pistons in the cylinder