Question

A car covers 30 km at an uniform
speed of 60 km/h and the next 30 km
at a speed of 40 km/h. Find the average
speed for the entire journey.​

Answer 1

Answer:

50 kilometers per hour

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Answer 2

$\sf{ \orange{\bigstar Given \longrightarrow }}$

• $\sf{Distance \ [s_1] = 30km }$

• $\sf{ Distance \ [s_2] = 30km }$

• $\sf{speed \ [ v_1] = 60km/h }$

• $\sf{Speed \ [v_2] = 40km/h }$

 

$\sf{ \red{\bigstar Find \longrightarrow }}$

Average speed -??

   

$\sf{ \blue{\bigstar Formulas \ used \longrightarrow }}$

$\boxed{\sf{Average \ speed = \dfrac{Total \ distance }{ Total \ Time } } }$

$\boxed{\sf{ Speed = \dfrac{ Distance }{ Time } }}$

where,

Time is donated by 't'

Distance 's'

Speed 'v'

     

$\sf{ \pink{\bigstar SoLution \longrightarrow }}$

Firstly we will find the total time,

we know,

$\sf{speed = \dfrac{distance} {time} }$

$\sf{Total \ time \ [t] = \dfrac{Total \ speed }{ total \ distance } }$

$\sf{t= \dfrac{30}{60}+ \dfrac{30}{40} }$

$\sf{ t =\dfrac{5}{4} }$

so the total time = $\sf{\dfrac{5}{4} h }$

so Now put the value in average speed we get,

$\sf{\implies Average \ speed = \dfrac{ 30+30}{ \dfrac{5}{4} } }$

$\sf{\implies Average \ speed = \dfrac{60}{5} \times 4 }$

$\sf{\implies Average \ speed = 12 \times 4 = 48 }$

   

 

$\green{\bf{\underline {\therefore Average \ speed \ is \ 48km/h }} }$

 

____________________________

Additional info-

To convert 48km/h to ---m/s

we know,

1km= 1000m

1h= 3600s

$\sf{1 \dfrac{km}{h} = \dfrac{1000}{3600}m/s = \dfrac{5}{18} m/s }$

$\sf{48km/h = \dfrac{5}{18} \times 48m/s }$

$\sf{48km/h = 13.33m/s}$

so, the average speed in m/s is 13.33m/s.

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