1. Speed, Velocity, and Acceleration
Motion
Speed, Velocity, and Acceleration

2. MOTION Motion is easy to recognize but can be hard to describe
The following quantities are used to describe motion: speed, velocity and acceleration
Each of these is a rate. A rate is a quantity divided by time.

3. Frames of Reference Object or point from which motion is determined
Most common is the
Earth
Motion is a change
in position relative to
a frame of reference

4. Describing motion?
If you and your friend are walking down the hall together at the same speed, in the same direction, are you moving relative to your friend?
Is your friend moving relative
to you?
Are either of you moving
relative to the Earth?

5. Answer:
You are NOT moving relative to your friend, and your friend is NOT moving relative to you. You both are moving relative to the earth.

6. Speed Speed is a measure of how fast something is moving.
It is the rate at which a distance is covered
Units of speed could be: km/h, m/s, mi/h, ft/s

7. Speed Definitions: Speed
The rate at which something moves a given distance.
Faster speeds = greater distances
General formula for speed:
Speed = distance / time

8. Speed Speed = Distance ÷ Time
Example: A car travels 300km in 6 hours. What is the speed of the car?

9. Answer: Speed = distance ÷ time Speed = 300km ÷ 6 hours
Speed = 50km/hr

10. Speed Practice Problems
1. How far can a plane travel if it flies 800km/hr for 9 hours?
2. How long does it take a ship to go 500 km if it travels at a speed of 50km/hr?

11. Answer D
S T D
800km ▪ 9hrs = 7200km hr

12. Answer D
S T
500
50 T
500km ÷ 50km = 10 hrs hr

13. Velocity Speed in a given direction.
Again , Speed in a given direction.
Velocity is speed in a give direction!!!!!

14. Velocity Practice Problem
1. What is the velocity of a boat that travels from Nashville to Huntsville (10 miles) in 15 minutes?

15. Answer Speed = distance ÷ time Speed = 10 miles ÷ 15 minutes
Speed = 0.67 mi/min
Velocity = 0.67 mi/min South

16. Acceleration Definition Formula
Acceleration is a measure of how quickly the velocity changes
Formula
a = Dv/t
What does the D mean? – The Greek letter
D represents change. D V means a change velocity.

17. Acceleration For its velocity to change, an object must accelerate.
An object accelerates whenever its speed or direction or both change.
Acceleration may be positive (increasing speed) or negative (decreasing speed).

18. The 3 Types of Acceleration
Speeding Up
Slowing Down
Turning

19. Acceleration at Constant Speed
An object moving in a circle at constant speed is always accelerating (changing direction).