Please Help Quick ASAP Hurry This is Physical Science Which statements best describe magnetic fields?
A. Magnetic fields need a conductor.
B. Magnetic fields must have only positive charges.
C. Magnetic fields have north and south magnetic poles.
D. Magnetic fields are always found in insulators.

Amarble, a bowling ball, a basketball, and a baseball are rolling across the floor at 10 m/s. which one has the greatest kinetic energy? the marble the bowling ball the basketball the baseball

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

Red light strikes a metal surface and electrons are ejected. if violet light is now used with a 10% greater intensity, what will happen to the ejection rate (number of ejected electrons per second) and the maximum energy of the electrons? a) greater ejection rate; same maximum energyb) same ejection rate; greater maximum energyc) greater ejection rate; greater maximum energyd) same ejection rate; same maximum energye) none of the above answers are correct