Question

A sprinter goes off the starting block for a 100-meter run and at that instant the second-hand of a stopwatch had pointed towards north. He touches the finishing line exactly after 12 seconds. In which direction did the second hand point when he just crossed the finishing line?

• A. 18° North of East
• B. 18° East of North
• C. 72° North of East
• D. 82° East of North

Hint:

Remember, when dealing with circular motion like this, you can proportionally calculate the movement of the second-hand with respect to time passed.

Answer 1

The Correct Option is B

Since the stopwatch's second-hand was initially pointing North, after 12 seconds the second hand will have moved in a clockwise direction. The second-hand of the stopwatch completes one full revolution (360°) in 60 seconds. So in 12 seconds, the second hand moves $\frac{360}{60} \times 12 = 72$ degrees. Starting from North, a clockwise movement of 72° gives us the direction 72° East of North. Hence, the direction when the sprinter crosses the line is 18° East of North.