Velocity and Speed
Speed
Speed is just a number which says how fast an object is moving. For example: the car was moving at a speed of 10 m/s.
Velocity
Velocity is a number and a direction. It says how fast the object is moving and in what direction.
For example: the car was moving at a velocity of 10 m/s south-east; or: the lift was moving with a velocity of - 3.6 m/s. (In the last example, the information about direction is in the minus sign: it tells us that the lift is
moving downwards.)
Average Velocity and Instantaneous Velocity
The average velocity* is the velocity* averaged over the whole journey.
The instantaneous velocity* is the velocity* at one instant of time.
Velocity
Question 1
A man runs after a bus. The bus is travelling at an average speed of 5 m/s. The man runs 25 m in 6 s. Does he catch the bus?
Question 2
What is the vertical axis in a distance-time graph?
Questoin 3
What does a steep line correspond to in a distance-time graph?
Question 4
If a car increases in velocity from +5 m/s to +15 m/s in three seconds, what is its acceleration?