Question

an athlete completes half of the circle of radius 2m in 5 sec. Then the average velocity of the athlete is​

Answer 1

$\color{darkblue}\underline{\underline{\sf Given-}}$

• Athlete completes half of circle
• Radius of circle (R) = 2m
• Time to Complete half revolution (t) = 5s

$\color{darkblue}\underline{\underline{\sf To \:Find-}}$

• Average Velocity .

➩ Average Velocity

$\color{violet}\bullet\underline{\boxed{\sf V_{av}=\dfrac{Displacement}{Time}}}$

Displacement is Shortest distance Travelled.

⛬ here Displacement will be = 2R

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀= 2 × 2

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀= 4 m

$\implies{\sf v_{av}=\dfrac{4}{5} }$

$\color{red}\implies{\sf v_{av}=0.8\:m/s}$

$\color{darkblue}\underline{\underline{\sf Answer-}}$

Average velocity of athelete is $\color{red}{\sf 0.8m/s}$.

Answer 2

Answer:

The diameter of the circular track is given as 200 m. That is, 2r=200 m.

From this radius is calculated as Radius, r = 100 m.

In 40 sec the athlete complete one round. So, in 2 mins and 20 secs, that is, 140 sec the athlete will complete = 140 / 40 = 3.5 (three and a half) rounds.

One round is considered as the circumference of the circular track.

The distance covered in 140 sec = 2πr×3.5=2×3.14×100×3.5=2200 m.

For each complete round the displacement is zero. Therefore for 3 complete rounds, the displacement will be zero.

At the end of his motion, the athlete will be in the diametrically opposite position. That is, displacement = diameter = 200 m.

Hence, the distance covered is 2200 m and the displacement is 200 m.