Question

A train starts from rest with an acceleration of 0.8m/s. Find its speed in km/h. when it has moved through 50m.​

Answer 1

Answer:

32.23 km/hr (approx.)

Explanation:

Given:

• Initial velocity (u) = 0 m/s   (as it started from rest)

• Acceleration (a) = 0.8 m/s²

• Distance travelled (s) = 50 m

To find:

• Speed, i.e, Final velocity (v)

(in km/h)

Method to find:

We can derive the final velocity by using the 3rd equation of motion.

v² = u² + 2as

⇒ v² = 0² + (2 * 0.8 * 50)

⇒ v² = 80 m/s

⇒ v = √80 m/s

⇒ v = 8.94427191 m/s

To convert the speed to km/hr;

1 m/s = (18/5) km/hr

⇒ 8.94427191 m/s = 18/5 * 8.94427191 km/hr

⇒ 8.94427191 m/s = 32.199378876 km/hr ≈ 32.23 km/hr

Other equations of motion:

• v = u + at

• s = ut + 1/2at²

Hope it helps!

Answer 2

Answer:

Explanation:

Given :

• Initial velocity (u) = 0 m/s
• Acceleration (a) = 0.8 m/s²
• Displacement (s) = 50 m

To Find :

• Final velocity of a train, v

Formula to be used :

• v² = u² + 2as

Solution :

★Final velocity of a train,

v² = u² + 2as

⇒ v² = 0² + 2 × 0.8 × 50

⇒ v² = 0.8 × 100

⇒ v² = 80

⇒ v = 8.9 ≈ 9

⇒ v = 9 m/s

{ Now, convert m/s into km/h }

⇒ v = 9 × 18/5

⇒ v = 1.8 × 18

⇒ v = 32.4 km/h

Hence, Final velocity of a train is 32.4 km/h.