<u>Answer:</u> It is so because they have different number of neutrons.
<u>Explanation:</u>
Isotopes are defined as the chemical species which have same number of protons but differ in the number of neutrons.
They have same atomic number but different atomic mass.
<u>For Example:</u> are the three isotopes of carbon.
The number of protons in all the three isotopes is same which is 6 and the number of neutrons in the three isotopes are 6, 7 and 8 respectively.
Hence, it is so because they have different number of neutrons.
The net force = -5 N
The direction : to the left(negative sign)
<h3>Further explanation </h3>Net force : the sum of all forces acting on an object
Force is a vector quantity that has both magnitude and direction,
We agree that the move up and to the right is a positive sign, while down and to the left is a negative sign.
The direction of the force (horizontal motion) is to the right (+32 N), and to the left (-37 N), so the net force :