How to Answer: A gear rotates at 5 rpm and interfaces with a smaller gear in a 10:1 ratio. How fast does the second gear spin? If the first gear applies 10N*m of torque, then what does the second gear experience?
Advice and answer examples written specifically for a Mechanical Engineer job interview.
36. A gear rotates at 5 rpm and interfaces with a smaller gear in a 10:1 ratio. How fast does the second gear spin? If the first gear applies 10N*m of torque, then what does the second gear experience?
How to Answer
Your interviewer will likely ask you situation- and knowledge-based questions to understand how well you are able to explain concepts to others. Be prepared for questions like this one by practicing a few possibilities ahead of time. In this case, gears are elements of power transmission systems that involve rotating elements with teeth that mesh together. If the gears are different diameters, then the two gears will experience different amounts of torque and will spin at different speeds. The key to solving this is to remember that rotational speed is inversely proportional to gear ratio, whereas torque has the opposite relationship (proportional). A smaller gear coupled with a larger gear will spin faster but carry a smaller rotational force.
Written by Jason Toby on October 12th, 2020
Answer Example
"The second gear would spin at ten times the speed of the first gear, or 50 rotations per second. This can be calculated by multiplying the larger gear's rotational speed by the gear ratio of 10-to-1. Conversely, the torque is calculated by dividing the larger gear's applied torque by the gear ratio, which yields 1 Newton-meter of torque."
Written by Jason Toby on October 12th, 2020