Interview Tech Teaser!! Engineering brain teasers are often asked in interviews, and the best ones reference everyday actions and designs than interviewees can immediately relate to!
Question: Imagine you take a broom and find the point along its width at which you can balance it on your finger and it remains balanced horizontally. If you cut the broom into two pieces at that point, do the halves weigh the same or is one heavier than the other (and if so, which)?
Answer: This question goes back to your introductory Statics class as it relates to free body diagrams, forces, and moments. To balance the broom successfully, you are locating the point at which the moments due to the force of gravity acting on the broom’s two ends are equal with respect to each side of the pivot point (your finger). The broom shaft is long and slender while the broom head is wide and short, so the pivot point to balance the moments must be close to the head. This means that at the point of balance, the moment arm to the center of mass on the broom head is much less than the moment arm to the center of mass of the shaft. But if the moments generated by the two sides are equal, then the lesser moment arm on the broom head side implies that its mass is more than that of the shaft side.
