When is momentum conserved?

a. it is conserved when only two objects collide; more than two objects can't conserve momentum.

b. it is always conserved.

c. momentum is conserved when the system is closed, which means there are no forces, like friction, acting on it.

d. momentum is never conserved.

Clothes dryer uses about 7 amps of current from a 240 volt line. how much power does it use?

What is the rate of change in a objects position?

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants