Roller Coaster Physics
Speed & Velocity
What’s the difference between Speed and Velocity?
• Speed:
Speed vs. Velocity
• The measure of how fast an object is moving
• Measured as distance traveled per unit of time
• Example: The car was going 75 miles per hour (mph)
• Velocity:
• Speed with direction
• Measured as distance traveled per unit of time AND direction
• Example: The car was going 75 miles per hour north
Speed = distance
time
distance
Velocity =
south
time
The 3 formulas for Speed, Time & Distance:
Remember them from
D
this triangle:
S T
Distance
Speed =
Time
Solving for Speed
Distance
Time =
Speed
Solving for Time
Distance = Speed x Time
Solving for Distance
A windsurfer travelled 28 km in 1 hour 45 mins.
Calculate his speed.
Distance
Time
Speed =
=
D
S
T
28
1•75
1 hour 45 mins
= 16 km/h
Answer: His speed was 16 km / hour
Calculating *Speed for the project
• Measure distance the object traveled
• Measure the time it took the object to travel distance
• Use the speed formula:
Speed = Distance (cm)
Time (s)
• Remember all speed measurements should be in cm/s
* This is an average speed for the distance being measured
Practice: Calculate average speed
• Distance: 150 m
• Time: 5 seconds
• Speed: distance / time
150 m
30 m/s
Speed Mini Lab
• You’re going to practice calculating the speed of a rolling marble.
• Partner up with someone you have not worked with yet
• Each pair will grab the following:
•
•
•
•
Piece of wood & index card
Marble (1 x each size)
Meter stick
Stopwatch
• You will set up a ramp and measure a full meter
• Roll the marble down the ramp and time how long it takes to go a meter
• Collect your data
Speed Mini Lab (continued)
Trial #
Distance (cm)
1
2
3
4
5
100 cm
100 cm
50 cm
35 cm
80 cm
Time (sec)
Speed (cm/s)