Baffling brainteaser asked in job interview leaves people stumped - can you solve it?

A mechanical engineer job applicant has been left baffled by an unexpected brainteaser during an interview.

The perplexed candidate couldn't work out the answer during or after the interview and hoped users could throw light on the problem.

They posted: "During an interview was asked this brainteaser I couldn't answer correctly, was wondering if anyone could help me out."

The riddle presented was: "You have two identical pucks that are slid across a frictionless surface at the same starting velocity. They have to cross a finish line at the same distance from the starting line.

"However, when puck A is slid, it slides across a 'dip' in the table but returns to the original height after the dip. Puck B slides across a completely level surface. Which reaches the finish line first?"

Debate fired up online as some suggested both pucks would simultaneously reach the finish line, while others argued for puck A's quicker arrival.

One user confidently explained: "Both reach at the same time. Since the horizontal distance and initial velocities are the same, the time taken should be the same too - by the kinematic equation: distance (in x) equals velocity(in x) *time."

A second user suggested: "Make the dip a flat horizontal down, a flat level at the bottom, and then an equal, flat horizontal back up. the horizontal component of the movement has an acceleration and then a deceleration the cos of the angle."

Meanwhile, a third user explained: "From what I understand from my analysis and others on here (I was wrong at first). Puck A arrives first because it accelerates on the way down the dip, and on the way up can only decelerate back to initial velocity, due to the 'rotational' deceleration being the only change in its velocity.

"So essentially puck A is speeding up for a bit then going back to normal, like temporarily accelerating in a vehicle, which negates friction with energy input into the system."