Straight, Zigzag, Round, and Fast - First Grade Science
Look around the playground during recess. A soccer ball rolls across the grass, a child swings back and forth on a swing set, a spinning top twirls on the pavement, and a runner darts left and right avoiding taggers. Everything that moves is exhibiting motion. Motion is the scientific word for a change in an object's position over time. Objects do not all move in the same way; depending on the direction and path they take, objects can move in straight lines, zigzag patterns, circular paths, back-and-forth oscillations, and at vastly different speeds.
Describing Position and Motion
To know if an object has moved, you must compare its position to another object that is standing still. A stationary reference point helps you observe change in location.
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| WORDS THAT DESCRIBE POSITION |
| |
| ABOVE / BELOW The kite is above the roof. |
| IN FRONT / BEHIND The dog is behind the fence. |
| NEXT TO / BESIDE The bicycle is beside the tree. |
| NEAR / FAR The school bus is far down the street. |
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When an object changes its position relative to a reference point, it is in motion. If a toy train starts next to a toy station and ends up five feet away, motion has occurred.
The Patterns of Motion
Scientists classify motion based on the path or pattern the object traces through space.
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| FOUR PATTERNS OF MOTION |
| |
| STRAIGHT LINE ZIGZAG PATTERN |
| ------------------> /\ /\ /\ |
| Moves directly forward / \/ \/ \ |
| without turning. Sharp turns changing direction repeatedly. |
| |
| CIRCULAR (Round & Round)BACK-AND-FORTH (Oscillating) |
| .---. <=================> |
| / \ Swings repeatedly past a center point; |
| \ / pendulums, playground swings, guitar strings|
| '---' |
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1. Straight-Line Motion
Straight-line motion occurs when an object travels directly along an uncurving path. A bowling ball rolling down a polished wooden lane, a train moving along straight tracks, or a dropped apple falling straight down to the floor exhibits straight-line motion.
2. Zigzag Motion
Zigzag motion involves moving in one direction and then suddenly cutting diagonally in another direction, alternating back and forth. Skiers carving down a snowy slope, football players dodging defenders, and water striders darting across a pond move in zigzag patterns.
3. Circular Motion (Round and Round)
Circular motion occurs when an object travels along a curved circular path or spins around a central point. The blades of a ceiling fan, the hands of a wall clock, a carousel horse, and the wheels of a rolling bicycle all move in circular motion.
4. Back-and-Forth Motion (Vibration / Pendulum)
Back-and-forth motion happens when an object swings or moves in one direction, stops, reverses direction, and returns along the same path over and over. A playground swing, a grandfather clock pendulum, a rocking chair, and a plucked violin string move back and forth.
Speed: Fast vs. Slow
Speed measures how fast an object moves, or how much distance it covers in a certain amount of time.
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| SPEED COMPARISONS |
| |
| FAST OBJECTS (Cover distance quickly)SLOW OBJECTS (Take lots of time)|
| - Soaring jet airplane (~550 mph) - Garden snail (0.03 mph) |
| - Cheeta sprinting across savanna - Box turtle crawling in grass |
| - High-speed bullet train - Glaciers moving inches/year |
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Factors That Affect Speed
An object's speed depends on the force applied to it and the friction of the surface it travels across. Pushing a toy car hard makes it go fast; pushing it gently makes it travel slowly. Rolling a ball across smooth polished wood allows it to travel fast, while rolling it across thick shaggy carpet creates friction that slows it down rapidly.
Chapter Review Exercises
Question 1: What is the scientific definition of motion, and how do you know an object has moved?
Question 2: Name the four major patterns of motion introduced in this chapter and give one real-world example of each.
Question 3: Describe the path taken by a playground swing as someone pumps their legs. What pattern of motion is this?
Question 4: What is speed, and what are two things that can cause a rolling toy ball to move faster or slower?
Solutions and Explanations
Solution 1: Motion is a change in an object's position over time relative to a stationary reference point. You know an object has moved if its distance or direction from a still object has changed.
Solution 2: The four patterns are: straight-line motion (a bowling ball rolling down a lane), zigzag motion (a skier dodging slalom flags), circular motion (a spinning Ferris wheel or clock hands), and back-and-forth motion (a swinging pendulum or rocking chair).
Solution 3: A playground swing travels forward in a smooth upward arc, pauses momentarily at the peak, reverses direction, swings backward in an arc, pauses again, and repeats. This is back-and-forth (oscillating) motion.
Solution 4: Speed is the measure of how fast an object covers distance. Two factors that change a ball's speed are the amount of force used to push it (stronger pushes increase speed) and the roughness of the surface it rolls across (rough surfaces create friction that slows it down).