Question

You plan a trip on which you want to average 91 km/h. You cover the first half of the distance at an average speed of only 49 km/h. What must your average speed be in the second half of the trip to meet your goal? Note that the velocities are based on half the distance, not half the time. km/hIs this reasonable? Yes No

Answer 1

Answer:

637 km/h, not reasonable

Explanation:

Total average speed = 91 km/h

Average speed of first half, v1 = 49 km/h

Let the average speed for the next half is v2.

Let the total distance is 2s.

Time taken for first half of the journey, t1 = s / v1 = s / 49

Time take for the next half of the journey, t2 = s / v2

The average speed is defined as the total distance traveled to the total time taken

$91=\frac{2s}{\frac{s}{49}+\frac{s}{v_{2}}}$

$\frac{s}{49}+\frac{s}{v_{2}}=\frac{2s}{91}$

$\frac{1}{v_{2}}=\frac{2}{91}-\frac{1}{49}$

[tex]\frac{1}{v_{2}}=\frac{7}{4459}

v2 = 637 km/h

This is very high speed which is not reasonable.