During a phase change, the temperature of a substance

a)decreases

b)increases

c)stays the same

The temperature remains same during the phase change.

Option C

Explanation:

The term “change of phase” is similar to “change of state”. When there is a change of substance from a state to the other state or phase, it is known as changes in its state. This change of state occurs due to the change of heat.

When a substance changes the phase, either the heat comes out or goes in the substance. Although there occur a change in the content of heat present in the substance, the temperature will not change. It remains constant.  When ice melts it becomes water and the water vaporizes which becomes water vapour.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s