A rigorous 7th grade science review lesson preparing students for the Unit 1 Interim Assessment, focusing on motion, forces, energy transformations, and scientific inquiry skills.
7th Grade Science IA Answer Key • Sections 1 & 2 Page 1 of 3
Teacher Resource • Scoring & Review Key
Sections 3 & 4: Energy Relationships & Experimental Design (Answers)
Target Assessment: Unit 1 IA
Section 3: Potential & Kinetic Energy (Answers) 4 Questions • 8 Pts Total
8. Height & Potential Energy
Greater PE: Rock Y (at 25 meters)
Justification: Both rocks have the same mass (15 kg). Potential energy increases directly with height (\(PE = mgh\)). Higher cliff = more stored PE.
9. Mass & Kinetic Energy
Comparison: Truck has 2× the KE of the car
Explanation: Both travel at the same speed (20 m/s). Since \(KE = \frac{1}{2}mv^2\), kinetic energy is directly proportional to mass. Doubling mass doubles KE.
10. Ramp Energy Transformations
Descent Changes: As the skater rolls down:
• PE decreases (height drops toward zero).
• KE increases (speed increases).
Gravitational PE is converted into KE.
11. Speed vs. Kinetic Energy
Correct Choice: C (Increases significantly)
Rationale: Kinetic energy depends on speed squared (\(v^2\)). Increasing speed increases kinetic energy dramatically.
The factor intentionally manipulated (vinyl, felt, sandpaper).
13. Dependent Variable (DV)
Correct Answer: Distance rolled (cm or m)
The physical outcome measured with the meter stick.
14. Controlled Variables (Accept Any 2)
1. Same toy car (same 120 g mass & wheels).
2. Same ramp height (25 cm release height).
3. Same release technique (released from rest, no push).
15. Evaluating Fair Tests
Key Idea: To ensure that only surface texture causes differences in roll distance. Changing ramp height would introduce a second variable (different initial potential energy and starting speed).
**Inquiry Skill Rubric for Teachers:
Ensure students clearly distinguish between the variable (property measured) and the tool. For example, "distance rolled" earns full credit, whereas "meter stick" does not.
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7th Grade Science IA Answer Key • Sections 3 & 4 Page 2 of 3
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Teacher Resource • Scoring & Review Key
Section 5: Data Analysis & Final Must-Know Check (Answers)
Model Statement: "As applied force increases, final speed increases."
Award full credit for direct relationship phrasing.
18. Numerical Evidence (Accept Any 2)
• At 2 N, speed is 1.0 m/s; at 4 N, speed increases to 2.0 m/s.
• At the maximum force of 10 N, the cart reaches 5.0 m/s.
Scoring Rule: Must include exact numbers AND correct units.
19. Explaining Discrepant Data
Scientific Explanation: Sandpaper creates more friction than smooth wood. This backward frictional force opposes motion, reducing net force and resulting in less acceleration and a lower speed (2.5 m/s vs 4.0 m/s).
Final Must-Know Check (Answer Key) 7 Pts Total
Balanced forces → net force = 0 N → motion has no / zero change.
Unbalanced forces always cause an object to accelerate (change speed or direction).
Under the same applied force: as mass increases, acceleration decreases.
At the exact same speed: as mass increases, kinetic energy increases (doubles).
As an object's height above ground increases, its potential energy increases.
When graphing data: IV goes on the x-axis; DV goes on the y-axis.
Strong scientific evidence must always cite actual numbers / data values with units from data.
0 12 24 0 4 7 10 Time (s) Distance (m) Seg 1 Seg 2 Seg 3
The graph shows the motion of an electric rover on a test track.
Part A: Calculate the average speed during Segment 1 (0 to 4 s):
Formula & Numbers:
Final Speed + Unit:
Part B: Which segment represents the rover at rest? Justify.
2. Net Force, Direction & Mass
A motorized supply cart with a mass of 10 kg is pushed across a warehouse floor. The motor exerts a 35 N force to the right, while friction exerts a 15 N force to the left.
Part A: Net Force & Direction
← 15 N
10 kg Cart
35 N →
Net Force:
Direction:
Part B: Changing Mass
If workers load 15 kg of cargo into the cart (mass becomes 25 kg) while the forces stay unchanged, what happens to the cart's acceleration? Explain why.
3. Newton's Third Law (Action-Reaction Forces)
A competitive swimmer pushes against the solid pool wall with a backward force of 75 N to launch into a turn. Which statement correctly describes the force exerted by the wall and the resulting motion?
A) The wall exerts 0 N because it is immovable and fixed in place.
B) The wall exerts an equal force of 75 N forward on the swimmer, accelerating the swimmer forward.
C) The wall exerts a smaller force of 25 N forward due to water resistance.
D) The swimmer's force cancels out the wall's force, so no movement can occur.
Correct Choice (Cross out 2 wrong choices first):
7th Grade Science • Unit 1 IA Morning-Work Packet Page 3 of 4
Practice & Wrap-Up • 11–30 Minutes
Section 3 (Part B) & Section 4: Final IA Strategies
Almost Ready • Build Your Confidence!
4. Potential & Kinetic Energy on a Track
A 0.4 kg steel ball is released from rest at Position A (height = 3.0 m). It rolls down through Position B (height = 1.0 m) to the flat floor at Position C (height = 0 m).
Part A: Energy at Position A vs. C
Where is gravitational potential energy at its maximum, and where is kinetic energy at its maximum?
Part B: Energy Conversion Explanation
Describe what happens to PE and KE as the ball travels from Position A to Position B:
5. Experimental Design & Variables
A science class investigates: "How does the surface material of a ramp affect the distance a toy truck rolls?" They test smooth plastic, coarse sandpaper, and corrugated cardboard, releasing the same 200 g truck from a 20 cm ramp.
Independent Variable:
Dependent Variable:
One Controlled Variable:
6. Engineering Challenge: Criteria vs. Constraints
An engineering team is challenged to build an earthquake-resistant tower. Label each design factor as either a Criterion (success goal) or a Constraint (limitation):
a. Total material cost must be under $12.00:
b. Must remain standing during 30 s on shake table:
c. Must be built using only 50 wooden craft sticks:
When circulating during minutes 6–11, look for students actively underlining:
• Motion Graphs: Horizontal line = at rest; Speed formula = change in distance ÷ change in time.
• Forces: Balanced forces = constant velocity OR at rest; Newton's 3rd Law = equal & opposite.
• Energy: Height ↑ = PE ↑; Speed ↑ = KE ↑; Downhill = PE converts into KE.
• Engineering: Criteria = goals; Constraints = limitations.
Part A (Speed Calculation):
• Two points on Segment 1: \((0\text{ s}, 0\text{ m})\) and \((4\text{ s}, 12\text{ m})\).
• Formula & Substitution: \(s = \frac{\Delta d}{\Delta t} = \frac{12\text{ m} - 0\text{ m}}{4\text{ s} - 0\text{ s}} = \frac{12}{4} = \mathbf{3\text{ m/s}}\).
• Common Trap: Forgetting the unit "m/s" or subtracting the axes backward.
Part B (At Rest Segment):
• Segment 2 (from 4 s to 7 s) represents the rover at rest.
• Justification: The line is completely horizontal/flat, which indicates the rover remains at position 12 m while 3 seconds of time elapse.
2. Net Force, Direction & Mass Key 2 Pts Total
Part A (Net Force Calculation):
• Net Force = \(35\text{ N (Right)} - 15\text{ N (Left)} = \mathbf{20\text{ N}}\).
• Direction = To the Right (in the direction of the larger applied motor force).
Part B (Mass vs. Acceleration):
• The cart's acceleration will decrease.
• Explanation: According to Newton's Second Law (\(a = F_{net} \div m\)), when force is constant, mass and acceleration are inversely related. Greater mass creates more inertia and resists acceleration.
3. Newton's Third Law (Action-Reaction Forces) Key 1 Pt
• Correct Choice: B (The wall exerts an equal force of 75 N forward on the swimmer)
• Diagnostic Rationale: Newton's Third Law dictates that every action force produces an equal and opposite reaction force. The swimmer applies 75 N backward onto the wall; the wall simultaneously applies 75 N forward onto the swimmer. Because the swimmer is free to move in water, this unbalanced forward force accelerates the swimmer forward.
• Distractor Alert: Choice D is a classic misconception—action and reaction forces act on different objects (one on the wall, one on the swimmer), so they do not cancel out!
Unit 1 IA Morning Facilitation Guide • Practice Solutions (Part A) Page 2 of 3
Teacher Resource • Practice Items 4–6
Practice Solutions (Part B) & Pre-Test Script
Target Assessment: Unit 1 IA
4. Potential & Kinetic Energy on a Track Key 2 Pts
• Part A: Maximum PE is at Position A (highest elevation, 3.0 m). Maximum KE is at Position C (lowest elevation, 0 m, where all PE has converted to speed).
• Part B: As the ball moves from A to B: PE decreases because height drops from 3.0 m to 1.0 m, and KE increases because gravitational potential energy converts into kinetic energy of motion.
5. Experimental Design & Variables Key 3 Pts
Independent Variable:
Ramp surface material (plastic, sandpaper, cardboard).
Dependent Variable:
Distance the toy truck rolls (measured with meter stick).
Controlled Variable (Any 1):
• Same 200 g toy truck
• Same 20 cm ramp height
• Same release method (no push)
6. Criteria vs. Constraints Key 2 Pts
a. Material cost under $12.00: Constraint
b. Stand 30 s on shake table: Criterion
c. Only 50 wooden craft sticks: Constraint
d. Hold 250 g weight at top: Criterion
Final Pre-IA Script & Transition Protocol (Min 28–30) Read Aloud to Class
"Pencils down. Put both feet flat on the floor, roll your shoulders back, and take one deep breath in... and let it out." (Pause 5 seconds)
"Look at what you just accomplished in 30 minutes. You calculated speed on a motion graph, balanced forces, predicted acceleration, traced energy transformations, and identified experimental variables. Everything on the IA is what we just practiced."
Remember the 3 Testing Rules:
1. Read the question twice and circle what it actually asks for.
2. Cross out 2 wrong choices before making your final pick.
3. Never leave a blank—if you get stuck, star it, guess your best, and keep your momentum going!
"You are completely ready. Trust your hard work. Put your morning packet in the corner of your desk, clear your workspace, and let's conquer this IA!"
Unit 1 IA Morning Facilitation Guide • Solutions (Part B) & Script Page 3 of 3
