A scientist designs some experiments to record how various substances change. She then reviewed her results. Which of the investigations listed below is an example of how the substance changed chemically? 1. Hydrochloric acid is stored inside plastic containers.
2. Sodium metal reacts violently and explodes with water.
3. After heating aluminum in a crucible, it began melting at 1200 degrees F
4. Grinding Copper sulfate allowed it to be dissolved much quicker.

Need asap ‼️ 20 pts which gravitational force field diagram is drawn correctly? (answers in pictures below)

(a) assume the equation x = at^3 + bt describes the motion of a particular object, with x having the dimension of length and t having the dimension of time. determine the dimensions of the constants a and b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.) (b) determine the dimensions of the derivative dx/dt = 3at^2 + b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.)

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.