Question

A women starts from home to office with a speed 5km/hr, 2.5 km away and be instantly returns to home with a speed 25 km/ hr . find total distance travelled , total displacement and average speed?​

Answer 1

ANSWER:

• Distance travelled = 5 km

• Total displacement = 0

• Average speed = 8.33 kmph

GIVEN:

• Initial speed = 5 kmph

• Distance of office from home = 2.5 km

• Final velocity = 25 kmph

TO FIND:

• Distance travelled

• Total displacement

• Average speed

EXPLANATION:

Distance travelled:

Distance travelled = 2 × Distance from office to home

Distance travelled = 2 × 2.5 km

Distance travelled = 5 km (or) 5,000 m

Total displacement:

The total displacement is zero. As she starts at her home and again returned to her home.

As both initial and final points are same displacement is zero.

Average speed:

$\boxed{\bold{\large{Avg \:speed = \frac{Total\: distance}{Total\:time}}}}$

$\boxed{\bold{\large{Time = \frac{Distance}{Velocity}}}}$

$Avg \:speed = \dfrac{2.5 + 2.5}{ \dfrac{2.5}{5} + \dfrac{2.5}{25} }$

$Avg \:speed = \dfrac{5}{ 2.5 \bigg(\dfrac{1}{5} + \dfrac{1}{25} \bigg)}$

$Avg \:speed = \dfrac{2}{\dfrac{5 + 1}{25}}$

$Avg \:speed = \dfrac{50}{6}kmph$

AVERAGE SPEED = 8.33 kmph

CONVERSIONS:

• 1 km = 1000 m

• 1 kmph = 1000/3600 m/s = 5/18 m/s

• 50/6 kmph = 50/6 × 5/18 = 250/108 m/s

• 50/6 kmph = 2.39 m/s