Question

The length of second hand of clock is 14cm, an ant sits on the top of second hand. find the following

Answer 1

Answer:

i) v = 1.47 cm/s

ii) distance = 219.8 cm

iii) displacement = 28cm

Explanation:

Remember that:

The motion of the tip of the second hand is a circular motion.

For something that rotates with an angular frequency ω, and a radius R, the velocity is given by:

v = ω*R.

i) We know that the second hand of a clock does a complete rotation each 60 seconds.

Then the period is:

T = 60s

And the frequency is the inverse of the period, so:

f = 1/T

f = (1/60s)

And the angular frequency is 2*pi times the normal frequency, thus:

ω = 2*pi*f

ω = 2*pi*(1/60s)  = (2*pi/60s)

And the radius will be 14 cm, the velocity of the ant is:

v = (2*pi/60s)*14cm

if we replace pi by 3.14 we get:

v =  (2*3.14/60s)*14cm = 1.47 cm/s

ii) The distance covered by the ant in 150 seconds:

Remember that the period of the clock is T = 60s

so in 150 seconds we have:

150s/60s = 2.5 revolutions.

Then the total distance covered is 2.5 times the perimeter of a circle of radius R = 14cm, this is:

distance = (2.5)*2*pi*14cm

              = (2.5)*2*3.14*14cm = 219.8 cm

iii) We want to know the displacement, this is, the difference between the final position and the initial position.

In 150 seconds, the ant does 2.5 revolutions.

So the ant will end in the opposite side of the circle where she started (if the ant started when the second hand was at the "3", then the final position is when the second hand is at the "9").

So the displacement will be equal to twice the radius, or the diameter of the circle.

if the radius is 14cm, the diameter is:

2*14cm = 28cm

the displacement is 28cm