2.2 Velocity & Average velocity

Displacement per unit time is called velocity.

               velocity=displacement time        v=∆x ∆t

Velocity is a vector quantity with magnitude and direction. The SI unit of velocity is meters per second (m/s).

Average velocity

The displacement divided by time interval is called average velocity.

Suppose a bus is moving along a road in a straight line. Consider that the positions of the bus are x1 at time t1 and x2 at time t2. In the time interval Δt = t2 – t1, the displacement of the bus is Δx = x2 – x1

Average Velocity – object accelerating at a constant rate

For an object moving with uniform acceleration (constant acceleration), the average velocity is equal to the average of the initial velocity (vi) and the final velocity (vf).

1. An athlete swims from the north end to the south end of a 50.0 m pool in 20.0 s and makes the return trip to the starting position in 22.0 s.

a. What is the average velocity for the first half of the swim?

b. What is the average velocity for the second half of the swim?

2. During a race on level ground, Ahmed runs with an average velocity of 8.2 m/s to the east. What is his displacement after 150 s?

3. During a race on level ground, Ahmed runs with an average velocity of 8.2 m/s to the east. What is his displacement after 150 s?

4. Reyan drives her car with an average velocity of 60.0 km/h to the east. How long will it take her to drive 300 km on a straight and smooth highway?