2.3 Speed and Velocity

Key Concepts

Speed

Measure of how fast an object is moving.

speed = distance / time

Scalar quantity
SI unit: meter per second (m/s)
No direction specified

Velocity

Speed with a specified direction.

velocity = displacement / time

Vector quantity
SI unit: meter per second (m/s)
Direction specified

Types of Speed and Velocity

Average Speed

Total distance covered divided by total time taken.

Average speed = total distance / total time

Instantaneous Speed

Speed at a particular instant of time.

Uniform Speed

Equal distances covered in equal intervals of time.

Variable Speed

Speed that changes over time.

Average Velocity

Total displacement divided by total time taken.

Average velocity = total displacement / total time

Instantaneous Velocity

Velocity at a particular instant of time.

Uniform Velocity

Equal displacements covered in equal intervals of time.

Variable Velocity

Velocity that changes over time (in speed or direction).

Interesting Facts

Usain Bolt's top speed: 10.44 m/s or 37.58 km/h
Slowest animal (3-toed sloth): 0.00134112 m/s or 0.0048 km/h
Fastest animal (Peregrine Falcon): 108.333 m/s or 390 km/h
Speed of light: approximately 3×10⁸ m/s
Speed of sound in air: approximately 343 m/s

Example Problems

Reaction Time of a Batsman

Problem: Shoaib Akhtar bowled at 161.3 km/h. If the batsman is 17.5 m away, what'sthe reaction time?

Solution:


                  1. Convert speed to m/s: 161.3 km/h = 44.8 m/s
                  2. Use time = distance / speed
                  3. t = 17.5 m / 44.8 m/s = 0.39 s

The batsman has 0.39 seconds to react.

Fastest Train in the World

Problem: Shanghai'sMaglev traveled 30 km in 7 minutes and 30 seconds. What'sits speed in km/h?

Solution:


                  1. Convert time to seconds: 7.5 min = 450 s
                  2. Calculate speed: 30,000 m / 450 s = 66.67 m/s
                  3. Convert to km/h: 66.67 m/s * (3600 s / 1 h) * (1 km / 1000 m)

The train'sspeed is 240.01 km/h.