Question

ncert class 9. chapter 8 - motion. 3) A train starting from a railway and moving with uniform acceleration attains a speed 40 km/h in 10 mins. Find its acceleration. the ans is 0.0185. ...and I used the formula [a= v-u/t] and my result is 0.185...i am not getting the zero...pls help me..if anybody can .
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Answer 1

v = 40km/h = (40*1000/3600) m/s= 11.111m/s

u = 0m/s , t = (10*60) s= 600 s

now ,

a = (v-u)/t = (11.111/600)m/s² = 0.0185 m/s²

perhaps u were not converting all the units to SI ..that might b the reason ...y your ans came wrong ...hope i am of some help to u ..brother

Answer 2

Given :

➳ Initial velocity = zero

➳ Final velocity = 40kmph

➳ Time interval = 10min

To Find :

➨ Acceleration of train.

Concept :

➢ Acceleration is defined as the rate of change in velocity.

➢ It is a vector quantity having both magnitude as well as direction.

➢ It can be positive, negative or zero.

➢ SI unit : m/s²

✴ First equation of kinematics :

$\bigstar\:\underline{\boxed{\tt{v=u+at}}}$

Conversion :

➠ 1kmph = 5/18mps

➠ 40kmph = 40 × 5/18 = 11.11mps

➠ 10min = 10 × 60 = 600s

Calculation :

$\longrightarrow\tt\:v=u+at\\ \\ \longrightarrow\bf\:a=\dfrac{v-u}{t}\\ \\ \longrightarrow\tt\:a=\dfrac{11.11-0}{600}\\ \\ \longrightarrow\underline{\boxed{\tt{a=0.0185\:ms^{-2}}}}$