Grade 3 Science Chapter 2 | Practice Workbook

Grade 3 Science: Practice and Assessment

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Lesson 1: Pushes, Pulls, and Motion

Investigation: With an adult, place a toy car on a clear, level floor and mark a starting line. Give it a gentle push and measure how far it travels from the line to where it stops. Repeat three times. Use the same car and surface. Record each distance in centimeters. Next try a stronger push three times, keeping other conditions as similar as possible. Do not use stairs or aim the car at anyone.

1. What is a force?

2. What reference point will you use for the car’s motion?

3. What changes between the two sets of trials?

4. Name two conditions to keep the same.

5. Record the three gentle-push distances with units. If you have not tested yet, leave this blank.

6. Compare the two sets of trials. Does your evidence support a difference? Explain; if untested, describe how you would compare.

Advanced extension: Explain why repeating trials helps, and identify one way the strength of a hand push might be difficult to keep consistent.

Lesson 2: Balanced and Unbalanced Forces

Investigation: Set a small book on a flat table. Gently push from opposite sides with one finger from each hand. Try to keep it still, then gently increase one push and observe. Repeat safely without pushing the book off the table. Feel and describe the pushes; this activity does not measure force precisely. Other forces, including friction, can also act.

1. What does balanced net force mean?

2. If an object is at rest and the net force stays zero, what happens to its motion?

3. Can a moving object have balanced forces? Explain.

4. Two opposite horizontal pushes are each 3 units. What is their combined horizontal force?

5. A 5-unit right push and a 2-unit left push act along the same line. What is their combined force?

6. Does a book that stays still prove no forces act on it? Explain.

Advanced extension: Explain how friction can keep a gently pushed box still even when only one person is pushing it.

Lesson 3: Patterns of Motion

Investigation: With an adult, place a short book under one end of a piece of sturdy cardboard to make a low ramp. On a clear floor, release a toy car from the same marked point without adding a push. Measure from the bottom of the ramp to the stopping point. Do three trials. Keep the ramp, car, surface and release point the same. Record actual measurements in centimeters and look for a pattern.

1. Why do you release the car from the same point?

2. Name the quantity to measure and its unit.

3. What are the three example distances in the worked model?

4. What is a reasonable prediction for a fourth model trial?

5. Record your three actual ramp distances, or leave blank until tested.

6. Use your measurements to predict another trial and state one reason it might differ.

Advanced extension: Test a second ramp height with adult help, keeping the car, release position relative to the ramp, and floor as consistent as practical. Compare repeated trials and identify a limitation.

Lesson 4: Magnets Can Act at a Distance

Investigation: With adult supervision, use a large classroom magnet and several objects, such as a steel paper clip, paper, a wooden craft stick and an aluminum foil ball. Predict for each object, then bring the magnet near it and record what you observe. Move the magnet slowly closer without touching the object and note whether it moves. Keep magnets away from electronics and medical devices. Never use small loose magnets around young children, and never put a magnet in the mouth.

1. Can a magnetic force act without the objects touching?

2. Do magnets attract every metal?

3. What can happen when two magnets are brought together?

4. What should you record before testing each object?

5. Record two actual results, or leave blank until you test.

6. What is one safety rule for this investigation?

Advanced extension: Design a comparison of magnetic attraction through paper and thin cardboard. Keep the magnet and target the same, and explain a fair way to compare distance.

Lesson 5: Solve a Problem with Magnetic Forces

Design challenge: With an adult, make a cardboard or folded-paper flap that can be opened and closed. Have the adult securely attach a large magnet and a suitable steel piece outside children’s reach, or describe a design on paper if safe materials are unavailable. Test whether the flap stays shut through three gentle tilts. Record each actual result, change one feature if needed, and retest. Do not use sharp tools without an adult. A drawing is a design proposal, not a completed test.

1. What problem is the example design trying to solve?

2. Name a success criterion for the example.

3. Name one constraint.

4. What magnetic interaction might hold the flap shut?

5. Record the results of your three actual trials or describe your untested design.

6. Suggest one improvement and explain how you would test it.

Advanced extension: Compare two latch designs with the same test. Explain how you would record reliability and why three trials may not be enough.

Independent Chapter Check

Use what you learned. For investigation questions, describe a plan if you have not performed the test. Do not invent results.

1. A 4-unit force pushes right and a 4-unit force pushes left along the same line. What is the combined force?

2. A moving object experiences zero net force. Describe its motion while net force remains zero.

3. A toy car travels 30, 32, and 31 cm in three imaginary trials. Predict a fourth trial and explain the uncertainty.

4. Can a magnet pull an object without touching it? Name a suitable example.

5. Describe a fair comparison for testing how a ramp height affects a toy car’s travel.

6. A magnetic latch fails one test. Give one improvement and describe how to retest.

7. Explain why recorded observations should not be invented.

8. Explain one magnet safety rule.