Total length of travel, from beginning to end. The distance is always positive.
Displacement, Δx, is the change in position:
Δx= xf - xi
Can be positive, negative, or zero.
Positive and Negative Displacement
of the displacement indicates the direction
- Δx>0 motion to the right
- 0<Δx motion to the left
Units (displacement & distance)
The SI unit of distance and displacement is the meter, m.
- Average speed is distance divided by elapsed time:
- average = distance/time
- Average velocity, vav, is displacement divided by time:
- 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.
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.
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.
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.
is the change in the velocity divided by the change in time.
- Its positive if Vf>Vi
- its negative if Vf<Vi
the limit of the average acceleration as the time interval goes to zero.
instantaneous acceleration is equal to the average acceleration.
an object whose speed is decreasing is said yo be decelerating. whenever V and acceleration have opposite signs.
in a v-versus-t plot, the instantaneous acceleration is equal to the slope of the tangent line at a given time.
The SI unit of acceleration is meters per second per second, or m/s^2
Acceleration due to gravity
varies slightly on the earths surface from place to place. Always a positive quantity.