Question

Four spheres start revolving clockwise in concentric circles from their initial positions as shown below. Yellow travels at 2m/sec, green at 4m/sec, red at 2m/sec and blue at 4m/sec. Which of the following statement(s) is/are TRUE?

• A. Yellow and green never cross (overtake) each other
• B. Red and blue takes the same time to complete one revolution
• C. Yellow takes less time than green to complete one revolution
• D. Blue and red will cross each other twice after the first 3 complete revolutions of blue

Answer 1

The Correct Option is A

The problem involves four spheres revolving in concentric circles at different speeds. Let's analyze the scenarios given: 

• Yellow and green never cross: Yellow travels at 2m/sec and green at 4m/sec. Since green is twice as fast as yellow, green will continually increase its distance from yellow. Thus, they will never cross each other.
• Red and blue take the same time to complete one revolution: Red travels at 2m/sec and blue at 4m/sec. If they travel different distances in the same time, they complete revolutions at different rates.
• Yellow takes less time than green to complete one revolution: Given that green is faster than yellow, green completes revolutions quicker, making this statement incorrect.
• Blue and red cross each other twice after the first 3 complete revolutions of blue: As blue is faster than red, it overtakes red multiple times, but the exact count depends on their respective circle lengths and speeds, which are not provided. Without more info, this statement cannot be confirmed.

Thus, the only valid statement is that yellow and green never cross each other.