Cam and follower selection for automotive valve gear: Which follower form is generally used in automobile engines for reduced wear at high speed? Assume mainstream production engines prioritizing durability, stable contact, and low sliding friction at the cam–tappet interface. Choose the correct option.

Given data

• Identify the commonly used follower in automobile engines.

Concept / Approach
Knife-edge → very high contact stress and wear; rarely practical.Flat/mushroom followers are used in some designs but have significant sliding.Roller followers minimize sliding, reduce wear, and suit high-speed cam profiles—commonly adopted in automotive valve trains.

Reasoning
Because the cam–follower contact experiences high Hertzian stress and speed, rollers are preferred to limit friction and wear while maintaining accurate timing.

Final Answer
Roller follower