Question

A car moves a distance of 100m. It covers first half with speed 10m/s and another half with speed v. If avg speed of car is 18m/s then value of v is

Answer 1

Explanation:

v= 90 m/s ....

Pihu ❤️ Sam

Answer 2

The car travels the another half part of the journey with a speed of 90 m/s.

Given,

Distance that the car covers=100 m

Speed for the 1st half of the journey=10 m/s

Speed for the another half of the journey=v m/s

Average speed of the car=18 m/s.

To find,

the value of v.

Solution:

• Average speed is equal to he ratio of the total distance covered to the time taken to cover it.

• Average speed is a scalar quantity.

Average speed=Total distance covered/Total time taken.

Time taken to cover the first half of the journey,

$Speed=\frac{Distance}{Time} \\10=\frac{50}{Time} \\Time=\frac{50}{10} \\Time=5 seconds.$

The car takes 5 seconds to cover the first 50 m.

Time taken to cover the another half of the journey,

$Speed=\frac{Distance}{Time} \\v=\frac{50}{Time} \\Time=\frac{50}{v} seonds.$

The car takes $\frac{50}{v}$ seconds to cover the another 50 m.

Average speed=Total distance covered/Total time taken

$18=\frac{100}{5+\frac{50}{v} } \\18=\frac{100}{\frac{50+5v}{v} } \\18=\frac{100v}{50+5v} \\18(50+5v)=100v\\900+90v=100v\\900=100v-90v\\900=10v\\v=\frac{900}{10} \\v=90 m/s.$

The value of v is 90 m/s.

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