Question

On a 120 km track, a train travels the first 30 km at a uniform speed of 30 km/h . calculate the speed with which the train should move rest of the track so as to get the average speed of 60 km/h for the entire trip?
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Answer 1

Given :

Length of the track = 120km

Train travels the first 30 km at a uniform speed of 30 kmph.

Average speed of train = 60 kmph

To Find :

The speed with which the train covers rest of the track.

Solution :

❖ Average speed is defined as the ratio of total distance travelled to the total time taken.

• It is a scalar quantity having only magnitude.
• SI unit : m/s

$:\implies\:\underline{\boxed{\bf{\orange{V_{av}=\dfrac{Total\: distance}{Total\:time}}}}}$

By substituting the given values;

$\sf\dashrightarrow\:V_{av}=\dfrac{d}{t_1+t_2}$

We know that, Time = Distance / Speed

$\sf\dashrightarrow\:60=\dfrac{120}{\left(\dfrac{30}{30}\right)+\left(\dfrac{90}{V_2}\right)}$

$\sf\dashrightarrow\:1+\dfrac{90}{V_2}=2$

$\sf\dashrightarrow\:\dfrac{90}{V_2}=1$

$:\implies\:\underline{\boxed{\bf{\gray{V_2=90\:kmph}}}}$

∴ The train should move at a speed of 90 kmph for rest of the track in order to get average speed of 60 kmph.

Answer 2

Answer:

your answer

Explanation:

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