An electric insulator is a material: A. Containing no electrons B. Through which electrons do not flow easily C. That has more electrons than protons on its surface D. Cannot be a pure chemical element

B.

Explanation:

The ability of a substance to conduct electricity depends on the free electrons it has.

An electric insulator is a material in which electrons have little freedom to move. For this reason, they are bad conductors of electricity and are used in producing insulating materials. They however contain electron.

Conductors on the other hand are materials whose electrons are very free to move. Hence they are very good conductors of electricity

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