What is the change in internal energy if 30 J of heat are released from a system and the system does 50 J of work on its surroundings?
Use u=Q-W

Suppose a wheel with a tire mounted on it is rotating at the constant rate of 2.15 times a second. a tack is stuck in the tire at a distance of 0.373 m from the rotation axis. noting that for every rotation the tack travels one circumference (a) find the tack's tangential speed. (b) what is the tacks radial acceleration?

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

How does the strength of the electrostatic force between an electron and a proton compare to the strength of the gravitational force between them?