# Fisica. One Dimensional Kinematics

 Distance Total length of travel, from beginning to end. The distance is always positive. Displacement Displacement, Δx, is the change in position: Δx= xf - xi Can be positive, negative, or zero. Positive and Negative Displacement The sign of the displacement indicates the direction of motion. Δx>0 motion to the right0<Δx motion to the left Units (displacement & distance) The SI unit of distance and displacement is the meter, m. Average Speed Average speed is distance divided by elapsed time:average = distance/time Never negative Average Velocity Average velocity, vav, is displacement divided by time:Vav=Δx/Δt=Δf-xi/tf-ti Positive if motion is in the positive direction.Negative if motion is in the negative direction. Units (velocity & speed) The SI unit of speed and velocity is meters per second, m/s. Instantaneous velocity The velocity at an instant of time is the limit of the average velocity over shorter and shorter time intervals: Can be positive, negative, zero, with the sign indicating the direction of motion. Constant Velocity When velocity is constant, the Graphical interpretation of velocity In a x-versus-t plot, the average velocity is the slope of a line connecting two points. Graphical interpretation in a x-versus-t plot, the instantaneous velocity at a given time is equal to the slope of a tangent line at that time. Average acceleration is the change in the velocity divided by the change in time. Its positive if Vf>Viits negative if Vf