Question

A train starts from rest and accelerates uniformly for 30 second to attain a velocity of 72 km/hr. Find its acceleration

Answer 1

Given

u = 0m/s

t = 30 second

v = 72km/hr = 72 × 5/18m/s = 20m/s

So a = (v - u)/t

a = 20-0/30

a = 2/3 m/s²


hope it helps dear friend ☺️✌️

Answer 2

Question: A train starts from rest and accelerates uniformly for 30 second to attain a velocity of 72 km/hr. Find its acceleration.

First let's define a few terms...

• Acceleration: Change in Velocity of an object is referred to as acceleration...

• Velocity: Speed of an object moving in a straight line is known as velocity...

In the given question, it is given that

• The train starts from rest, ie., Initial Velocity(u) = 0 m/s
• Time(t) = 30 s
• Final Velocity(v) = 72 km/h

...and, we need to find the acceleration of the object. But, before we do that, we need to change every thing to standard units.

• The standard unit of time is s...and,
• Of Velocity/Speed is m/s...

Here, Final Velocity(v) = 72 km/h ..... to change from km/h to m/s, multiply the number by $\frac{1000}{3600}$ or $\frac{5}{18}$.

Therefore, $72 \: km/h = \frac{72 \times 1000}{3600} = \frac{72 \times 5}{18} = \frac{360}{18} = 20 \: m/s$

Acceleration is defined as rate of change in velocity.

Here, change in velocity, ie., v-u = 20-0 = 20 m/s

Rate of change of velocity = $\frac{ Change \: In \: Velocity }{ Time }$ = $\frac{20}{30} = \frac{2}{3} = 0.66 \: m/s^2$

Therefore, acceleration = 0.66 m/s²....