Question

(Please answer my question from second paragraph. The main Q is not the problem for now.)

A train increases its speed steadily from 10 m/s to 20 m/s in 1 minute. (a) What is its average speed during this time, in m/s? (b) How far does it travel while increasing its speed?

My teacher says the answer to (a) is ​​​​​​​​​10m/s
(without using any formulas or explanations, she just makes us choose between 10 or 20m/s.) and for (b) she makes us write down a sentence ​​​I dont recall anymore. I'm wondering if she is correct or not because​​​​​​​​ every answer I found on the internet contradicts her​​​​​​ ​otherwise. ​​​​​

Answer 1

Answer:

See below

Explanation:

from 10 m/s to 20 m/s  

         average is   (10 + 20 )/2 = 15 m/s average

15 m/s  * 60 sec = 900 meters

Here is a longer way to find out how fa it travelled

  a = acceleration = change in velocity/ change in time

                             =   10 m/s / 60 sec = 1/6 m / s^2

xf = xo + vo t + 1/2 a t^2

   = 0   + 10 (60) + 1/2 ( 1/6)(60)^2

   =            600    + 1/12 (3600) = 900 meters