Question

1.a)A train travels the first 75 km at a uniform speed of 50 km/h; the next 10 km at a uniform
speed of 20 km/h and the last 15 km at a uniform speed of 30 km/h. Calculate the average speed

for the whole journey.

b) Define average speed and write it’s S.I. unit.​

Answer 1

Answer:

a) Average speed of body is 40 km/h .

b) Definition of Average speed : Average speed of body is defined as the total distance covered by the body divided by time taken to cover the total distance.

SI unit of Average speed : m / s

Explanation:

given,

• Train travels first 75 km at uniform speed of 50 km/h
• next 10 km at a uniform speed of 20 km/h
• last 15 km at a uniform speed of 30 km/h

To find,

• Average speed of Train

so,

Using formula

time = distance / speed

Time taken by train to cover a distance of 75 km at speed of 50 km/h, t₁ = ?

→ t₁ = 75 / 50

→ t₁ = 3 / 2  hrs

Time taken by train to cover a distance of 10 km at speed of 20 km/h, t₂ = ?

→ t₂ = 10 / 20

→ t₂ = 1 / 2 hrs

Time taken by train to cover a distance of 15 km at speed of 30 km/h, t₃ = ?

→ t₃ = 15 / 30

→ t₃ = 1 / 2  hrs

therefore,

→Total time taken for the journey, t = t₁ + t₂ + t₃

→ t = ( 3 / 2 ) + ( 1 / 2 ) + ( 1 / 2 )

→ t = 5 / 2 hrs

And,

→ total distance covered by Train, s = 75 + 10 + 15

→ s = 100 km

so,

Using formula

• Average speed = total distance covered / total time taken

→ Average speed of train = s / t

→ Average speed of train = 100 / ( 5 / 2 )

→ Average speed of train = 40 km/h

hence,

• Average speed of train is 40 km/h.

Answer 2

Answer:

40 km per hour

Explanation:

the answer for you two questions is 40 km per hour.SI unit is km per hour

hope this question is understood by you

thank you

Enjoy your life with happiness