Forces and Motion — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A book sitting still on a table has unbalanced forces.
Corrected: A book sitting still on a table has balanced forces.
Grade 3 Science teaches that objects at rest have balanced forces acting on them.
2. Fix the sentence:
In a tug of war that is tied, the forces are unbalanced.
Corrected: In a tug of war that is tied, the forces are balanced.
Grade 3 students learn balanced forces are equal and opposite, causing no motion change.
3. Fix the sentence:
A ball rolling downhill shows balanced forces.
Corrected: A ball rolling downhill shows unbalanced forces.
Grade 3 learners know unbalanced forces change an object's motion, like speeding up a ball.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. When forces are equal and opposite, they are balanced forces.
In Grade 3 Science, balanced forces cancel out and keep objects at rest or moving steadily.
2. When one side pushes harder than the other, forces are unbalanced.
Grade 3 learners know unbalanced forces cause objects to speed up, slow down, or change direction.
3. A book sitting still on a table has balanced forces acting on it.
Grade 3 Science explains that resting objects have gravity balanced by the table pushing up.
4. A ball rolling downhill is moved by unbalanced forces.
Grade 3 students see unbalanced forces create motion changes like acceleration downhill.
Part C: True or False?
Read each statement. Circle True or False.
1. Balanced forces cause no change in motion in Grade 3 Science lessons.
True False
Grade 3 learners discover balanced forces leave an object's motion unchanged.
2. A tied tug of war shows unbalanced forces in Grade 3 examples.
True False
A tied tug of war has equal forces, so Grade 3 Science calls them balanced.
3. Unbalanced forces can make a ball roll faster in Grade 3 Science.
True False
Grade 3 students learn unbalanced forces change speed, like a ball rolling downhill.