Scoring Guide: Forces & Motion

Read each question. Circle the answer or write it on the lines.

1. 1.

   Jen drags a sled up a snowy hill by its rope. Is she using a push or a pull?

   (1 pt)

   Answer: pull

2. 2.

   A soccer ball rolls toward Zoe. She kicks it back the way it came. What did her kick do to the ball's motion?

   (1 pt)

   Answer: It changed the ball's direction (it may also change its speed).

3. 3.

   Which one can a force NOT do to an object?

   (1 pt)

   Answer: change it into a different object

4. 4.

   A bird feeder hangs still from a branch on a rope. The rope pulls up on the feeder. What force pulls the feeder down? Are the forces on the feeder balanced or unbalanced? How do you know?

   (3 pts)

   Answer: Gravity pulls it down. The forces are balanced, because the feeder is not moving (the pull up equals the pull down).

5. 5.

   Theo tosses a ball straight up. It slows down, stops for a moment and falls back to his hand. What force pulls it back, and which way does that force pull?

   (2 pts)

   Answer: Gravity; it pulls down (toward the ground).

6. 6.

   A box sits still on the floor. Mia pushes it to the right, and Sam pushes it to the left, but Mia pushes harder. a) Which way does the box move? b) The next day, the box is sitting still again. Mia and Sam push on it from opposite sides, equally hard. Does the box move? Why?

   (2 pts)

   Answer: a) To the right (the way Mia pushes). b) No, it stays still, because the forces are balanced (equal pushes in opposite directions).

Read about Kayla's test. Use the table to answer questions 7 to 10.

1. 7.

   Rank the surfaces from LEAST friction to MOST friction.

   (2 pts)

   Answer: kitchen counter, cardboard, rubber bath mat

2. 8.

   In Kayla's test, what is the one thing she changed? Name one thing she kept the same.

   (2 pts)

   Answer: She changed the surface. Kept the same: any one of the same book, the same push (the launcher), or the same way of measuring.

3. 9.

   Kayla says, "Smooth surfaces have less friction than bumpy ones." Do her results support her claim? Claim: ____ Evidence: ____ Reasoning: ____

   (6 pts)

   Answer: Answers vary. Look for: Claim: yes, her results support it. Evidence: the book slid 31 inches on the smooth counter but only 9 inches on the bumpy bath mat. Reasoning: friction slows a moving object, so the surface with less friction lets the book slide farther; the smooth counter still had some friction, because the book stopped.

4. 10.

   Why do people sprinkle sand on an icy sidewalk?

   (2 pts)

   Answer: Sand adds friction, so shoes grip and people do not slip.

Think about forces that can act without touching. Use the table for question 14.

1. 11.

   Two ring magnets are slid onto a pencil. The top magnet floats above the bottom one without touching it. Which poles are facing each other? How do you know?

   (2 pts)

   Answer: The same poles (north and north, or south and south). Like poles repel, so the top magnet is pushed up.

2. 12.

   Which object will a magnet attract?

   (1 pt)

   Answer: a steel screw

3. 13.

   Write C for a contact force or N for a non-contact force. ___ a magnet pulls a nail across a small gap ___ a bat hits a baseball ___ gravity pulls a falling leaf down ___ a rubbed plastic comb lifts bits of paper ___ your hand pushes a door open

   (2 pts)

   Answer: N, C, N, N, C

4. 14.

   Ana used the magnet in the table. What pattern do you see? Predict: with 8 layers, will the magnet hold more clips or fewer clips than with 6 layers?

   (3 pts)

   Answer: The more layers (the farther the magnet is from the clips), the fewer clips it holds, because its pull gets weaker. With 8 layers it will hold fewer clips (maybe none).

5. 15.

   Jae rubs a balloon on his hair. It picks up tissue bits from 1 inch away but not from 6 inches away. Write one cause-and-effect question he could test next.

   (2 pts)

   Answer: Answers vary. Look for: a testable question that changes one thing and looks at one effect, such as "Does rubbing the balloon more times let it pick up tissue from farther away?" or "How close must the balloon be to lift the tissue?"

6. 16.

   A magnet is held above a paper clip on a table. The clip jumps up and sticks to the magnet. Name the force pulling the clip up and the force pulling it down. Which force was stronger? How do you know?

   (3 pts)

   Answer: Up: the magnet's pull. Down: gravity. The magnet's pull was stronger, because the clip moved up (the forces were unbalanced).

Use what you see to predict what will happen next. Use the table for questions 17 and 18.

1. 17.

   Lin lets a marble go near the rim of a big bowl. It rolls back and forth. The table shows how high it rolled up the side each time. Predict how high it will roll on Roll 5.

   (1 pt)

   Answer: 4 cm

2. 18.

   If the marble keeps rolling, what will it do in the end? Use the pattern to explain.

   (2 pts)

   Answer: It will stop at the bottom of the bowl, because each roll goes 2 cm lower than the one before (friction keeps slowing it).

3. 19.

   Kai's pendulum has a string 40 cm long. He changes to a string 15 cm long. Will it make more swings or fewer swings in 30 seconds? Why?

   (2 pts)

   Answer: More swings, because a shorter string makes a pendulum swing faster.

4. 20.

   Ana and Ben ride a see-saw. Ana's end is down right now. Where is Ben's end? What happens next when Ana pushes off the ground?

   (2 pts)

   Answer: Ben's end is up. Next, Ana's end goes up and Ben's end comes down; the up-and-down pattern repeats.