The average speed of a train is 24.0km/hr. Suppose a train moving at this speed accelerates -0.20 m/s^2 until it reaches a speed of 8.0 km/hr. How long does it take the train to undergo this change in speed?

Explanation:

The initial speed of train = 24 km/hr = 24 x 1000/3600 = 20/3 m/sec

The final speed of train =  8 km/hr = 8 x 1000/3600 = 20/9 m/sec

The relation of motion

v = u + a x t

final velocity = initial velocity + acceleration x time

20/9 = 20/3 - 2 x t   where t is time

Because the acceleration is negative

2 t =  20/3 - 20/9 = 40/9   or  t = 20/9 sec = 2.2 sec

The time taken to decrease the speed from 24 km/hr to 8 km/hr is 2.2 sec approx

b) phosphorus pentoxide

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this