Speed & Acceleration
On a graph showing distance versus time, a ___________________ line represents an object that is not moving at all.
horizontal
Position
location of a particular object
the SI unit of acceleration
m/s²
Deceleration/negative acceleration
means an object is slowing down
Accelerate
means an object is speeding up
Steady Velocity
means an object's acceleration is zero
Speed
measure of how quickly an object's position changes
Good reference point
must be an object that is fixed (does not move) compared to the motion you are trying to describe.
On a velocity-time graph, a line slanted DOWN from left to right shows ______________ acceleration
negative
Acceleration
rate at which velocity changes; acceleration measures a change in velocity
If you know how far someone travelled (their distance) and how long they travelled for (their time), then you can use this information to calculate their __________.
speed
Velocity
speed that also includes direction
International system of units
used by scientists all over the world
Two people can walk at the same speed but have a different ________ . EXAMPLE: •Mr. Neblung walked South at 100 m/s •Mr. Sidrow walked West at 100 m/s
velocity
Slope
the steepness of a line on a graph
Units of measure for time:
• hours • minutes • seconds
Units of measure for distance:
• meters per second (m/s) • kilometers per second (km/s) • kilometers per hour (km/h)
units of measure for average speed:
•meters per second/second (m/s²) •kilometers per second/second (km/s²) •kilometers per hour/hour (km/h²)
Reference point
an object that appears to stay in one place
True or False: I will be prepared to look at a distance-time graph and use it to figure out when an object was moving the fastest.
True
Motion
a change in position over time
If an object begins to move faster but does NOT change direction, then its speed will ___________. EXAMPLE: If I continue driving in the same direction but start to drive faster, we would say that my speed is _________________.
accelerate; accelerating
Be able to apply the formula for calculating acceleration:
acceleration = final velocity - initial velocity/time
Heily sits in a moving plane. As she looks out the window, another plane is right next to hers. When she looks again, the other plane is STILL right next to hers. What does this tell us about the speed of the two planes?
ANSWER: The other plane is moving at the same speed as Heily's plane
Two objects traveling at the same speed have different velocities IF they move in __________.
Answer: different directions.
Sample Acceleration Problem: A train accelerates from 0 m/s to 70 m/s in 5 seconds. What is the acceleration?
SOLUTION: acceleration = 14 m/s²
What are the steps you take in order to solve a word problem using the speed formula?
Step 1: Draw your triangle: Step 2: Draw a second, blank triangle:Step 3: Read the world problem. • Underline the GIVEN information. • Circle the information you still need to find. • Ask yourself: have they given me... -speed and time? -distance and time? -distance and speed? Step 3: Using the given information, fill in your blank triangle to figure out whether you need to: • divide distance by speed • divide distance by time • multiply speed by time Step 4: Use your calculator to solve the problem.
