Holden is trying to determine the velocity of his race car. He went 20 meters east, turned around, and went 40 meters west. His car was 20 meters from the starting line. This took 5 seconds.

Question

What is the car’s average velocity?

4 m/s east
4 m/s west
12 m/s west
12 m/s east

Answer 1

To find the average velocity of Holden's race car, we use the formula for average velocity:

\[ \text{Average Velocity} = \frac{\text{Displacement}}{\text{Time}} \]

1. Calculate the displacement:

   • Holden first travels 20 meters east and then turns around to travel 40 meters west.
   • Displacement is the final position relative to the starting position.
   • After traveling 20 meters east, he turns around and travels 40 meters west.
   • His final position is \( -20 \) meters from the starting position (20 meters east is positive and 40 meters west is negative).
   • Thus, the displacement is:

   \[ \text{Displacement} = -20 , \text{meters} \]

2. Calculate the time:

   • The total time taken for the journey is 5 seconds.

3. Calculate average velocity:

   • Now we can calculate the average velocity:

   \[ \text{Average Velocity} = \frac{-20 , \text{meters}}{5 , \text{seconds}} = -4 , \text{m/s} \]

The negative sign indicates that the direction of average velocity is west.

Thus, the average velocity of the race car is 4 m/s west.