Basics of MotionSpeed

Velocity

(t) Time is always positive◦ Measured in seconds (s)

(d) Distance is always positive◦ Measured in meters (m)

(s) Speed is always positive◦ Measured in meters per second (m/s)

◦ Formula:

Scalar Variables

( d) Displacement can be positive or negative◦ Measured in meters (m)◦ Takes direction into account (+ or -)◦ If you start where you end, then d = 0

( v) Velocity can be positive or negative◦ Measured in meters per second (m/s)◦ Takes direction into account (+ or -)◦ If you start where you end, then v = 0

◦ Formula:

Vector Variables

1. During track practice, your friend runs 100 m in 12 s. Calculate his speed.

2. Assuming that your friend’s speed is constant, how long will it take him to run 1600 m?

3. What will your friend’s displacement be when he completes one lap around the track?

Examples

4. The black mamba is one of the world’s most poisonous snakes, and with a maximum speed of 5.0 m/s it is also the fastest. Suppose a mamba waiting in a hideout, sees prey and begins slithering toward it with a velocity of 7.6 m/s. After 2 s, the mamba realizes that its prey can move faster than it can. The snake then turns around and slowly returns to its hideout in 14.2 s. Calculate:

The mamba’s average velocity during its return to the hideout.

The mamba’s average velocity for the complete trip.

More Examples