Question

A body moves first 80km/h in 2 hours and next 70 km. in one hour. it's average speed is (in km.p.h)​

Answer 1

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A body moves first 80 km in 2 hours and next 70 km in one hour. Calculate it's average speed in km/h.

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$\sf{D_1 = 80 \: km}$

$\sf{T_1 = 2 \: hours}$

$\sf{D_2 = 80 \: km}$

$\sf{T_2 = 1 \: hour}$

${ \sf{Total \: Distance = D_1 + D_2}}$

$\sf{Total \: Distance = (80 + 70) \: km}$

$\sf{Total \: Distance = 150 \: km}$

Now,

$\sf{Total \: Time = T_1 + T_2}$

$\sf{Total \: Time =( 2 + 1) \: hours}$

$\sf{Total \: Time = 3 \: hours}$

Using formula for calculating Average speed,

$\sf{Average \: speed = \dfrac{Total \: distance \: travelled}{Total \: time \: taken} }$

$\sf = \dfrac{150}{30} \: km/h$

$\sf = 50 \: km/h$

∴ Average speed of body =

$\green{ \underline{ \boxed{ \sf{ \gray{ 50 \: km/h}}}}}$

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Average Speed:

The ratio of the total distance travelled by the body to the total time taken by the body to cover the distance is called average speed.

Instantaneous Speed:

If the speed of a body is continuously changing with time, then the speed at some particular instant during the motion is called instantaneous speed.

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