Question

A sprinter goes off the starting block for $100m$ 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. ${18}^o$ North of East
• B. ${18}^o$ East of North
• C. ${72}^o$ North of East
• D. ${82}^o$ East of North

Answer 1

The correct option is A ${18}^o$ North of East

When he starts running, the second-hand of a stopwatch had pointed towards North.

Clock has ${360}^o$, so every 15 seconds make an angle of ${90}^o$.

So, $1$ second has $6^o$.

After 12 seconds, it will make an angle of $12\times 6={72}^o$.

As after every 12 seconds he touches the finishing line, so as he crosses the finishing line he makes an angle of ${72}^o$.

And hence, ${18}^o$ North of East.

Hence, option A is correct.