Which of the following substances is a compound?
a.
solid bronze (an alloy of copper and tin)
b.
a salt water solution
c.
solid iron metal (fe)
d.
hydrogen sulfide gas (h2s)

D. hydrogen sulfide gas (H2S)

Explanation:

A compound is composed of two or more elements chemically bound together.

In this case, hydrogen is chemically bounded with sulfur to form a gaseous compound called hydrogen sulfide.

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