The infant’s smile that appears whenever mother peeks over the side of the crib and makes a funny face is called

The answer to this question is a social smile. A social smile is a smile from babies which is a response from babies to somebody's smile. The babies smile is said to be a milestone on his or her development. Social smile from babies can be seen and observed during the babies from 6 to 8 weeks old. Making the babies smile is a bonding moment between the parent and the child.

the more kinetic energy there is, the hotter it will get due to friction