What is the change in internal energy if 30 j of thermal energy is released
from a system, and the system does 40 j of work on the surroundings? use a
u= q-w.

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

Acharge q experiences no net force at a particular point in space. which of the following situations described below must always be true? -there are no other charges nearby. -if there are other charges nearby, they must all have the same sign as q. -if there are other charges nearby, they must all have the opposite sign of q. -if there are other charges nearby, the total positive charge must equal the total negative charge. -none of the above

First to answer will be the brainliest i need the answer asap