Question

(1 Point)

A truck's speed increases uniformly from 15 km h to 60 km/h in 20 s. Determine (a) the average
speed

Answer 1

0.625 m/s

General Formulas and Concepts:

Unit 0

• SI unit (distance) - meters
• SI unit (time) - seconds

Kinematics

• Average Speed Formula:
  `\displaystyle (total \ distance)/(time)`

Step-by-step explanation:

Step 1: Define

[Given] Initial speed: 15 km/h

[Given] Final speed: 60 km/h

[Given] time: 20 s

[Solve] Average speed

Step 2: Convert

Initial speed

1. Set up conversion:
   `\displaystyle (15 \ km)/(h)((1000 \ m)/(1 \ km))((1 \ hr)/(60 \ min))((1 \ min)/(60 \ s))`
2. Multiply/Divide [Cancel out units]:
   `\displaystyle (25)/(6) \ (m)/(s)`

Final speed

1. Set up conversion:
   `\displaystyle (60 \ km)/(h)((1000 \ m)/(1 \ km))((1 \ h)/(60 \ min))((1 \ min)/(60 \ s))`
2. Multiply/Divide:
   `\displaystyle (50)/(3) \ (m)/(s)`

Step 3: Solve

1. Set up:
   `\displaystyle ((50)/(3) \ (m)/(s) - (25)/(6) \ (m)/(s))/(20 \ s)`
2. Subtract:
   `\displaystyle ((25)/(2) \ (m)/(s))/(20 \ s)`
3. Divide:
   `\displaystyle (5)/(8) \ (m)/(s)`