Our understanding of the atom has changed over time. which idea that was once accepted is now considered scientifically inaccurate

An engineer designs a roller coaster so that a car travels horizontally for 152 ft, then climbs 137 ft at an angle of 34.0° above the horizontal. it then moves 137 ft at an angle of 48.0° 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.)

What are atoms of the same element with varying number of neutrons

If an athlete runs once around a track, back to the starting line, her average velocity is zero. true or false?