25 points
1)state what is meant by the term physical change,
2)state what is meant by the term internal energy,
3)state what is meant by the term specific latent heat.

pshyical change is a usually reversible change of a substance, as size or shape: Freezing a liquid is a physical change. Compare chemical change.

internal change is when the movement of the particles increases

specific latent heat is the amount of energy per kg (unit mass) required to change ice to water without change in temperature.

less than one you can't create energy

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.