CALC The potential energy of a pair of hydrogen atoms separated by a large distance x is given by U(x) = -C6/x6, where C6 is a positive constant. What is the force that one atom exerts on the other? Is this force attractive or repulsive?

Solution 34E The potential energy is, C 6 U = x6 We can get the force from this potential as, U C 6 6 6C6 F = x = x( x6) = C ×6 x5 = x5 This is the force an atom exerts on the other. 5 The minus sign indicates that, the force is an attractive force. But the x term in the denominator says that, as the distance between the atoms increases, the force decreases. So, it is an attractive force.