A cyclist driving at 36, km h^{-1} stops his cycle in 2, s by application of brakes. Calculate (i) r

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7. MOTION

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A cyclist driving at $36\, km h^{-1}$ stops his cycle in $2\, s$ by the application of brakes. Calculate $(i)$ retardation $(ii)$ distance covered during the application of brakes.

Option A

Option B

Option C

Option D

Solution

$u=36 km h ^{-1}=10 m s ^{-1} ; v=0 ; a=? ; S =?$

$(i)$ Applying $\quad v=u+a t$

$0=10+a \times 2$

Therefore, $a=-\frac{10}{2}=-5 m s ^{-2}$

Retardation $=-($ acceleration $)$

$=-\left(-5 m s ^{-2}\right)$

$=+5 m s ^{-2}$

$(ii)$ Applying $v^{2}-u^{2}=2 a S$

$0-(10)^{2}=2 \times(-5) \times S$

$S=\frac{-100}{-10}=10 m$

Standard 9

Science

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