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Answer 1

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packer

packer

22.06.2018

Physics

Secondary School

+5 pts

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A train travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h. Calculate the average speed for the entire train journey.

Solution :

Question 40:

A train travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h. Calculate the average speed for the entire train journey

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SmãrtyMohït

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Here is your solution

Given :-

First 15 km at a uniform speed of 30km/h.

Next 75km at at a uniform speed of 50km/h.

Last 10km/h at a uniform speed of 20km/h.

Time 1st = distance /speed = 15/30

Time 2nd = distance /speed = 75/50

Time 3rd = distance /speed = 10/20

Total distance = 15km+75km+10km = 100km

Hence,

Average speed of train is 40km/h

Hope it helps you

Answer 2

In 1st 15 km car travels at a speed of 30km/h ==

$speed \: = distance \frac{time \\ time \: = \: distance \frac{speed \\ t1 \: 15 \frac{30 \: = \: 1 \frac{2h}{?} }{?} }{?} }{?}$

In next 75 km car travels at a speed of 50km/h ==

$t2 \: = 75 \frac{50 \: = 3 \frac{2h}{?}$

In last 10 km car moves at a speed of 20km/h ==

$t3 \: = \: 10 \frac{20 \: = 1 \frac{2h}{?} }{?}$

Total distance covered = 15+75+10 = 100 km/h

Total time taken = 1/2+1/2+3/2 = 2.5 h

So, average speed = 100/2.5 = 40km/h