A man performed 500 J of work moving a couch in his living room. It took him 10 seconds to move the couch. What was his power?  A. 50 W  B. 490 W  C. 5000 W  D. 100 W

According to newton’s first law of motion, which force is expected to cause a body to accelerate?

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

In a classical model of the hydrogen atom, the electron moves around the proton in a circular orbit of radius 0.053 nm. what is the electron's orbital frequency? what is the effective current of the electron?