8th grade unit 1 Force and Motion Graphs

Force and Motion Graphs

by Richard Thomas

​Graphs of motion are crucial for physicists to determine the position and speed of an object. Unlike maps and speedometers which are useful for non-physicists, graphs provide a detailed analysis of an object's movement over time. Motion seems to be essential in our lives as well as influences so many of our activities.

​So why are motion graphs important?

​A quick review before motion graphs are covered.......

Motion

Position is relative to an origin.
Example: "Ken is behind Barbie and Barbie is behind Ken."

Position is not the same as distance. It just describes "where"

Speed and Velocity

• Speed = Distance/Time

• When you divide the total distance of a trip by time you get the average speed

• Distance and displacement are not the same. Distance is covered ground and displacement is moving from a place or position.

• Instantaneous Speed is the actual speed at a given moment.

Graphs of Motion

Constant speed means the speed stays the same

Constant speed will look different on a position vs. time graph and a speed vs. time graph

Motion Graphs

Multiple Choice

What does the horizontal line represent in this graph?

• Resting, not moving

• a constant speed

• acceleration

• velocity

Multiple Choice

Acceleration occurs when an object changes its speed or ______.

• direction

• force

• inertia

• mass

Multiple Choice

Which runner stopped for a rest?

• Albert

• Bob

• Charlie

Multiple Choice

Which runner won the race?

• Albert

• Bob

• Charlie

Multiple Choice

How long did one of the runner's rest?

• 8 seconds

• 13 seconds

• 5 seconds

• 50 seconds

Multiple Choice

Velocity is

• speed and acceleration

• constant speed

• a frame of reference

• speed in a given direction

Multiple Choice

Acceleration is

• increasing speed

• decreasing speed

• changing direction

• all of the above

Multiple Choice

A car driving at 50 miles per hour drives for 2 hours. What distance did it cover?

• 50 miles

• 25 miles

• 100 miles

• 75 miles

Multiple Choice

What does this graph represent?

• Constant speed

• Acceleration

• Not moving

Multiple Choice

What does this graph represent?

• Constant Speed

• Acceleration

• Not moving

Multiple Choice

What does this graph represent?

• Constant speed

• Acceleration

• Not moving

Multiple Choice

What is happening between 2 and 3 seconds?

• The object is not moving.

• The object is not accelerating.

• The object is slowing down.

• The object is speeding up.

Multiple Choice

What is happening between 3 seconds and 4 seconds?

• The object is moving in a negative direction.

• The object is returning to its starting position.

• The object is slowing to a stop.

• The object is changing direction.

Multiple Choice

What is happening at E?

• Stationary

• Accelerating

• Fast steady speed; moving away from the starting position

• Steady speed; returning to start position

Multiple Choice

Which runner had a head start?

• A

• B

• C

Multiple Choice

 Every morning, Tom walks along a straight road from his home to the bus stop. Below, is a graph representing Tom’s trip to school. - What is the distance covered through the second segment, which is between 50 seconds, and 70 seconds?

• 40 meters

• 60 meters

• 80 meters

• 20 meters

Multiple Choice

Which graph shows the object standing still?

• A

• B

• C

• D

Multiple Choice

What is this line of this graph showing?

• moving away from starting point at a constant speed

• moving back towards the starting point at a constant speed

• acceleration (getting faster)

• deceleration (getting slower)