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OKLAHOMA ACADEMIC STANDARD FOR SCIENCE:
MS-PS2-2 MOTION AND STABILITY: FORCES & INTERACTIONS
8TH GRADE
OBJECTIVE:
Students who demonstrate understanding can plan an investigation to provide evidence that the change in an object’s
motion depends on the sum of the forces on the object and the mass of the object. (Newton’s First and Second Laws)
NOTE: Explanations of stability and change in natural or designed systems can be constructed by examining the
changes over time and forces at different scales.
CORE IDEAS:
1. The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not
zero, its motion will change.
2. The greater the mass of the object, the greater the force needed to achieve the same change in motion.
3. For any given object, a larger force causes a larger change in motion.
CLARIFICATION STATEMENT:
Emphasis is on balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces,
mass and changes in motion (Newton’s Second Law), frame of reference and specification of units.
ASSESSMENT BOUNDARY:
Assessment is limited to forces changing the motion in one-dimensional interactions (vertical or horizontal) in an inertial
reference frame. Only change one variable at a time. Assessment does not include the use of trigonometry.
MATERIALS REQUIRED:
•
Gravitate Kit
o
o
o
2 rubber hoses
Braces
Legs
•
Measuring Tape
•
Balls of varying sizes and weights
•
Scale (for weighing balls)
•
Stopwatch
MS-PS2-2: Energy
PREPARATION:
1. Set up the track.
2. Record measurements:
a. Measure and record the track length L. _____m
b. Measure and record the track height H. _____m
c. Measure and record the mass of the ball(s) M. _____kg
PROCEDURE:
Core Idea #1: The motion of an object is determined by the sum of the forces acting on it; if the total force on
the object is not zero, its motion will change.
Note: Guide the students through the first experiment; then let them conduct experiments.
Ask the students to write down each step of each experiment.
1. Choose 2 balls of equal mass and volume.
2. Place one ball at the beginning of the track and the other at the bottom of the hill.
3. Ask the students:
a. What is the net force on each ball?
b. Which of Newton’s Laws does this support?
4. Start the stopwatch as both balls are released simultaneously. If the top of the track is flat, you may need to give
them a gentle push.
a. Ask the students to list any evidence they observe that supports Newton’s Second Law.
b. Ask the students to write about their observations of force before and after releasing the balls.
c. Ask the students to document and verbalize their deductions or conclusions drawn from this evidence.
5. Repeat steps 2 through 4 releasing the balls from different elevations.
6. Repeat steps 2 through 4 using balls of varying mass.
Assess: Ask questions to help the students identify evidence of Newton’s First and Second Laws. Where might
they see Newton’s First and Second Laws in action in their daily life?
2
MS-PS2-2: Energy
Core Idea #2: The greater the mass of the object, the greater the force needed to achieve the same change in
motion.
Note: Guide the students through the first experiment; then let them conduct experiments.
Ask the students to write down each step of each experiment.
1. Record the weight of 2 balls of very different mass.
2. Place the lighter ball (ball 1) at the top of the hill and the heavier ball (ball 2) at the bottom of the hill.
3. Release the ball at the top of the hill. If the top of the track is flat, you may need to give it a gentle push.
4. Measure the distance ball 2 travels.
a. Ask the students to list any evidence they observe supporting the statement that the greater the mass of the
object, the greater the force needed to achieve the same change in motion.
b. Ask the students to tell you what deductions or conclusions they can draw from this evidence.
5. Repeat steps 1 through 4 allowing the students to conduct the experiment. Try using balls of varying mass in
various positions.
Assess: Ask questions to help the students identify evidence of this principle. Where might they see this
principle in their daily life?
Core Idea #3: For any given object, a larger force causes a larger change in motion.
Notes: In this exercise students will demonstrate understanding of impulse and its relation to Newton’s 2nd Law.
Guide the students through the first experiment; then let them conduct experiments.
Ask the students to write down each step of each experiment.
1. Record the masses of 2 balls of very different weights.
2. Place the lighter ball (ball 1) at the top of the hill and the heavier ball (ball 2) at the bottom of the hill.
3. Start the stopwatch as you release the ball at the top of the hill. If the top of the track is flat, you may need to
give it a gentle push.
4. Stop the stopwatch when ball 1 hits ball 2. Record the time _____ s.
5. Measure the distance ball 2 travels _____ m.
6. Repeat steps 2 through 5 pushing ball 1 a little harder each time.
a. Ask the students to list any evidence they observe supporting the statement that the greater the mass of the
object, the greater the force needed to achieve the same change in motion (Newton’s 2nd Law).
b. Aside from pushing strength, how else can we know whether the force is larger or smaller?
c. Ask the students to write about and verbalize their deductions or conclusions based on this evidence.
7. Repeat steps 2 through 6 using the heavier ball at the top of the hill and the lighter ball at the bottom.
Assess: Ask questions to help the students identify evidence of Newton’s 2nd Law. Where might they see this
principle in their daily life?
3
MS-PS2-2: Energy
Mass of Balls (kg)
1.
Ball 1:
Ball 2:
2.
Ball 1:
Ball 2:
3.
Ball 1:
Ball 2:
4.
Ball 1:
Ball 2:
5.
Ball 1:
Ball 2:
6.
Ball 1:
Ball 2:
7.
Ball 1:
Ball 2:
8.
Ball 1:
Ball 2:
9.
Ball 1:
Ball 2:
10.
Ball 1:
Ball 2:
11.
Ball 1:
Ball 2:
12.
Ball 1:
Ball 2:
13.
Ball 1:
Ball 2:
14.
Ball 1:
Ball 2:
15.
Ball 1:
Ball 2:
16.
Ball 1:
Ball 2:
Evidence Observed
4
Deductions and Conclusions