Question

A moving train is brought to rest within 20 seconds by applying brakes.Find the initial velocity if the retardation due to brakes in 2m/s²
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Answer 1

GIVEN :–

• A moving train is brought to rest within 20 seconds by applying brakes.

• Retardation is 2 m/s².

TO FIND :–

• Initial velocity = ?

SOLUTION :–

• We know that –

$\\ \implies \bf \large{ \boxed{ \bf v = u + at}}$

• Here –

$\\ \: \: {\huge{.}} \: \: \bf v = 0$

$\\ \: \: {\huge{.}} \: \: \bf u = ?$

$\\ \: \: {\huge{.}} \: \: \bf a = - 2 \: \: m/ {s}^{2}$

$\\ \: \: {\huge{.}} \: \: \bf t = 20s$

• Now put the values –

$\\ \implies \bf 0=u+( - 2)(20)$

$\\ \implies \bf u+( - 2)(20) = 0$

$\\ \implies \bf u - 40= 0$

$\\ \implies \large{ \boxed{ \bf u = 40 \: \: m/s}}$

Answer 2

$\bf \large{ \underline{ \underline{ \blue{question : }}}}$

A moving train is brought to rest within 20 seconds by applying brakes.Find the initial velocity if the retardation due to brakes in 2m/s²

$\bf \large{ \underline{ \underline{ \blue{answer : }}}}$

• Final velocity (v)=0
• Time taken (t)=20 s
• Acceleration (a)=-2 m/s²

From the equation:-

v=u+at , we have

u=v-at

$\bf \large \implies \: u = 0 - ( - 2) \times 20 \\ \\ \bf \large \implies \:u = 40 \: m {s}^{ - 2}$