🔍 Key Concepts

• Look at how the cam lobe in figure B is shaped compared to a perfect circle – the ‘fat’ side versus the ‘steep’ side shows how fast the follower (and valve) moves. • Think about what a gradual rise on the cam profile does to valve motion (slow, smooth lift) versus a sharp drop-off (quick, abrupt closing). • Relate the direction of rotation (arrow) to which side of the cam controls valve opening and which side controls valve closing (reseating).

💭 Think About

• As the cam in figure B turns in the direction of the arrow, does the follower climb up a long, gentle ramp or a short, steep ramp to reach full lift? What does that mean for how quickly the valve opens? • When the cam rotates past maximum lift, does the follower drop off the lobe quickly or follow a long, gentle slope down? What does that tell you about how the valve reseats? • Which choice best matches a cam that has an asymmetric shape – one side long and gradual, the other side short and steep – in terms of opening versus closing speed?

✅ Before You Answer

• Verify which side of the cam (leading edge vs trailing edge, relative to the arrow) corresponds to valve opening and which to valve closing. • Check whether figure B shows a long, gradual arc on the approach to maximum lift or on the return to the base circle – that tells you which action is slow. • Before picking an answer, confirm that your choice clearly states which part is slow (opening or reseating) and which part is abrupt/quick, matching what you see on figure B.