Organized procedure to study something under controlled conditions

Haley rubs a cotton cloth along a plastic strip. the plastic strip becomes positively charged. why did this happen? a. the plastic strip gained protons from the cotton. b. the plastic strip lost protons to the cotton. c. the plastic strip gained electrons from the cotton. d. the plastic strip lost electrons to the cotton.

An engineer designs a roller coaster so that a car travels horizontally for 162 ft, then climbs 127 ft at an angle of 31.0° above the horizontal. it then moves 127 ft at an angle of 46.0° below the horizontal. if we take the initial horizontal motion of the car to be along the +x-axis, what is the car's displacement? (give the magnitude of your answer, in ft, to at least four significant figures and give the direction of your answer in degrees counterclockwise from the +x-axis.)

Un jugador de beisbol batea un foul recto en el aire.la pelota deja el bate con una rapidez de 120 km/h. en ausencia de resistencia del aire. ? cual sera la rapidez de la pelota cuando la atrape el catcher