Question

a body is moving along the circumference of a circle with uniform speed. If it takes 20sec to complete one revolution. What is the displacement of particle after 45sec is

Answer 1

Answer:

See this question deals with circular motion with constant speed.

Now, as per the question, the time to complete one full revolution is 20secs.

To find out the displacement in 45 secs, follow this trick:

Since 1 revolution takes 20 seconds, two revolutions will take 40 seconds.

so we have 45 -40 secs = 5 seconds left.

In the 5 secs the object will complete quarter circle.

you can easily say this by unitary method.

20 seconds for 1 revolution

therefore 5 seconds for 1/4 revolution.

Now look at the photo.

For the first 2 revolution, starting point and ending point is same, so displacement is zero.

For the last 5 seconds apply Pythagoras theorem.

Considering radius to be R ,

The answer is R√2.

Answer 2

Answer:

√2r  where r is radius of the circle

Explanation: