Question

3. If a girl runs around a circular track of length 400m and comes back to
the initial point in 40s, what would be her speed and velocity.
7 point
O speed 25m/s,velocity 10
O speed 29m/s, velocity o
speed 10m/s, velocity 0
O speed 10m/s, velocity 10​

Answer 1

Given :

➳ Length of circular path = 400m

➳ Girl comes to the initial position after 40s.

To Find :

• Speed
• Velocity

Concept :

➨ Speed is defined as the ratio of total distance travelled to the total time taken.

➨ Velocity is defined as the ratio of displacement to the time.

➨ Distance is defined as the actual length of path which is covered by moving body (scalar).

➨ Displacement is defined as the shortest distance b/w initial and final position of entire journey (vector).

Calculation :

✴ Speed of Girl :

⇒ Speed = Distace/time

⇒ Speed = 400/40

⇒ Speed = 10m/s

✴ Velocity of Girl :

⟶ Here, Displacement of girl will be zero because she comes to the initial position after the given interval of time.

➢ Velocity = Displacement/time

➢ Velocity = 0/40

➢ Velocity = 0 m/s

Answer 2

Distance is the actual path travelled by the body between its initial and final position .It is a scalar quantity

Distance covered by the girl in order to cover the length of the circular track = 400 m

time taken = 40 sec

We know that ,

$\implies{speed = \frac{distance}{time} }$

$\implies{speed = \frac{400}{40} }$

$\boxed{speed =10 \frac{m}{s} }$

Displacement is a vector quantity . It is the shortest distance travelled by the body between its initial and final position

As the initial and final position of the girl is the same

displacement = 0

we know that ,

$\implies{velocity = \frac{displacement}{time} }$

$\boxed{velocity = 0}$