A tire swing hanging from a branch reaches nearly to the ground. How could you estimate the height of the branch using only a stopwatch?

Explanation:

With the help of expression of  time period of pendulum we can calculate the height of the branch . The swinging tire can be considered equivalent to swinging bob of a pendulum . Here length of pendulum will be equal to height of branch .

Let it be h . Let the time period of swing of tire be T then from the formula of time period of pendulum

 where l is length of pendulum .

here l = h so

If we calculate the time period of swing of tire , we can calculate the height of branch .

The time period of swing of tire can be estimated with the help of a stop watch . Time period is time that the tire will take in going from one extreme point to the other end and then coming back . We can easily estimate it with the help of stop watch .

answer: b.

explanation:

the higher the current the higher the mag field around it the higher the influence on the compass