Which term describes the amount of heat needed to change 1 kg of a substance from solid to liquid at its melting point?

This is specific latent heat of fusion.

This is the heat needed to turn 1 kg of solid into a liquid at its melting point. When a substance changes its state from  solid to liquid form or from liquid to gas , heat energy is needed. This energy is used not to heat the substance but to separate the molecules from each other.

This energy is called latent heat energy. While a liquid is boiling and while a solid is melting, there is no temperature change. The temperature only changes when the change of state is complete.

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