1. Exploring motion and forces
Chapter 3
Exploring motion and forces

2. Speed s = d/t Speed is the rate of change of distance
The relationship between distance, speed, and time is shown in the equation:
s = d/t
Where d = distance, s = speed, and t = time

3. Units for Speed Time = Distance = Speed = seconds meters
Meters/seconds

4. Finding: Speed, Time and Distance
Since we know the equation s = d/t, how do we find either distance or time given the other two amounts?
- by using simple algebra we can see that if given s and t:
d = s * t
- and if given s and d:
t = d/s

5. Instantaneous Speed: speed at a given instant
Average Speed: speed over a lot of time
Can find by total distance
total time

6. Examples:
A sprinter ran at a speed of 10m/s for 320m, how long did it take him to run that far?

7. Examples:
Example: a car traveled at 24 km/hr for 30 min., how far did the car travel?

8. In Albany a semi-truck gets pulled over for going 45 mph in a 55 mph zone. His driver’s license is later revoked.
Why?

9. Velocity Velocity describes both: Speed and direction
So, velocity describes speed in a given direction. To have the same speed and velocity, an object must be traveling both in the same direction and have the same speed.

10. Just like speed!
The relationship between distance, velocity, and time is shown in the equation: v = d/t
Where
v = velocity (m/s)
d = distance (m)
t = time (s)

11. Acceleration Acceleration is the rate of change of velocity.
It measures how much velocity is changing every SECOND
Equation for acceleration is:
Any change in velocity will cause an object to accelerate

12. Units for Acceleration
Equation:
Acceleration = Change in Velocity / time
a = Δv/t
Because: v = m/s (so is Δv)
t = s
then: a = m/s/s

13. Example:
Determine your average acceleration if your car starts out with a speed of 0 m/s and ends up with a speed of 10 m/s 20 seconds later.