Question

25 meter long car running at 30 km speed. it will take how time to cross at lamp post

Answer 1

Sᴏʟᴜᴛɪᴏɴ :-

We know That, when any moving object, cross a tree, Electric pole , standing man or lamp post it will cover distance equal to length of object in crossing .

So, we can conclude That ,

→ Speed = 30km/h .

→ Distance = 25m.

→ Time = (D/S).

And, we Also, know That,

→ 1km = 1000m.

→ 1Hour = 60 * 60 = 3600 seconds.

Therefore,

→ car cover (30*1000)m in = 3600 seconds.

→ car cover 1 m in = (3600/30000) seconds.

→ car will cover 25m in = (3600/30000) * 25 = 3 seconds.

Hence, The Car will cover The Lamp Post in 3 Seconds.

Answer 2

Note :

            When an object crosses  something like electric pole , tree ,

person , .... etc , then distance is equals to length of the object .

______________________________

Here given that ,

Length = Distance = 25 m

Speed = 30 km/h = 30 * (5/18) = 8.33 m/s

Time = ?

We know that ,  $\bold{\bf{\red{Speed=\;\frac{Distance}{Time} }}}$

⇒ 8.33 = 25 / ?

⇒ ? = 3 ( approximately )

Hence , Time , t = 3 sec

Hence the car take 3 seconds to cover lamp post

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More Information :

To convert km/h to m/s , we need to multiply the speed with 5/18.

Reason :

$\bold{\frac{1\;km}{1\;h}=\frac{1*(1000m)}{1*(60\;min)} =\frac{1000}{60*60}m/s=\frac{5}{18}m/s}$