If the train can slow down at a rate of 0.625 m/s2, how long, in seconds, does it take to come to a stop from this velocity?

66.28 s

Explanation:

Step 1:

Acceleration,a=

Time,t=9.75 min=

1 min=60 s

Initial velocity,u=

We have to find the final velocity of train.

We know that

Substitute the values

Step 2:

Now, initial velocity,u=41.425m/s

Deceleration,a=

Because the train velocity decreases

Final velocity, v=0

Again, substitute the values in the above formula

Hence, the train takes 66.28 s to come to stop from velocity 41.425m/s.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.