Which of the situations described below is explained by the electrical force A) A compass needle swings around so that it points due north
B) A rock sits at rest on the side of a hill, despite the gravitational force.
C) A child's hair stands on end after she removes a stocking cap on a cold day.
D) A race car traveling around a curve is pressed down into the banked track.​

Plzz worth 10 ! which statement about energy transformations is not true? a all forms of energy can be transformed into thermal b energy is never destroyed or created during transformations c potential chemical energy always transforms into kinetic d some thermal energy is always released during a transformation

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.

At a certain instant after jumping from the airplane a, a skydiver b is in the position shown and has reached a terminal (constant) speed vb = 52 m/s. the airplane has the same constant speed va = 52 m/s, and after a period of level flight is just beginning to follow the circular path shown of radius ρa = 2330 m. (a) determine the velocity and acceleration of the airplane relative to the skydiver. (b) determine the time rate of change of the speed vr of the airplane and the radius of curvature ρr of its path, both as observed by the nonrotating skydiver.