Motion in One Dimension Displacement and Velocity

Motion One dimensional motion is the simplest form of motion –Train on a straight track Can move forward or backward, not right to left or up and down

Motion Motion takes place over time and depends on frame of reference –Train is moving on its track while the Earth is rotating around its axis and revolving around the sun –Frame of reference – a coordinate system for specifying the precise location of objects in space Measure movement with respect to a frame of reference –Disregard other motion outside of frame of reference In train example, usually won’t care about motion of Earth, Sun, etc.

Displacement Displacement – the change in position of an object –Symbol is d or Δx –Displacement = change in position = final position – initial position –Δx=x f -x i

Displacement Displacement does not necessarily equal to total distance traveled Displacement can be positive or negative –Positive = to the right, forward, or up –Negative = to the left, backward, or down

Velocity Average velocity – the total displacement divided by the time interval during which the displacement occurred Velocity = displacement/time v= Δx/t

Velocity Velocity has both speed 55 m/s, 30 km/h, 100 mm/year And direction North, up, right, standing still, toward Temple –40 m/s North, 80 km/h straight up

Velocity Velocity is not the same as speed –Speed has magnitude only –Velocity has magnitude and direction –They are calculated very similarly v=d/t v=Δx/t In velocity, Δx=displacement In speed, d=distance

Velocity Distance-time graphs – When you graph the distance an object travels versus time, the slope of the line is the object’s speed or velocity

Velocity Average velocity is not the same as instantaneous velocity Instantaneous velocity – the velocity of an object at some instance (or specific point in its path) –Some distance/time graphs produce a curve instead of a straight line –To find velocity on a curve, draw a line tangent to the curve at the point of interest

Velocity