Grade 3: Motion

Lessons at a Glance

**Big Idea:** Motion is movement. You can describe an object’s
motion by how long it takes, how far the object travels, how fast the object
goes, and what path it follows.

Children contemplate what motion is as they become “motion detectives” who search for, identify, and describe motion in their surroundings. They think of words to describe motion and act out a variety of motions with their bodies, incorporating aspects such as distance, time, speed, change in speed, and path of motion in their demonstrations.

**Big Idea:** Motion is movement. You can describe an object’s
motion by how long it takes, how far the object travels, how fast the object
goes, and what path it follows.

Children act out different motions with their bodies and then depict motion in a drawing. They try to incorporate some of the components of motion—such as time, distance, speed, and path—in their drawings.

**Big Idea:** Motion is movement. You can describe an object’s
motion by how long it takes, how far the object travels, how fast the object
goes, and what path it follows.

Children focus on the path of motion, using their bodies and a ball to create and describe different paths. By comparing different paths between the same points, they learn that a good description of an object’s motion includes information about its path.

**Big Idea:** Motion is movement. You can describe an object’s
motion by how long it takes, how far the object travels, how fast the object
goes, and what path it follows.

Children investigate and compare the speeds of various motions they make with their bodies. They move in different ways (jumping, walking backwards, and crawling) for a fixed amount of time and measure how far they travel doing each motion. Building on this activity, the children compare the speeds of different motions and begin to develop an understanding that speed is determined by factors of time and distance.

**Big Idea:** The way to change how something moves is to give
it a push or a pull.

Children begin an extended study of how forces (pushes and pulls) change an object’s motion. They use toy cars and other props to discover that pushes and pulls are needed to get a still object to start moving. They also learn that pushes and pulls are required to change the direction of an object’s motion, and they contemplate other changes in motion, such as slowing down and speeding up.

**Big Idea:** The way to change how something moves is to give
it a push or a pull.

Children explore the effects of forces of varying sizes on the motion of toy cars. They discover that big forces change the motion of toy cars more than little forces do.

**Big Idea:** Collisions cause pushes that may change the motion
of all the colliding objects.

Children continue their investigation of forces by performing controlled collision experiments with marbles rolling along a track. By varying several factors, the children begin to realize they can change the strength of the forces involved in the collisions. They also identify conditions that make a marble roll partway along a track and those that make it roll all the way to the end of the track.

**Big Idea:** Collisions cause pushes that may change the motion
of all the colliding objects.

Children use the marbles and tracks from Lesson 7 to create controlled collisions and observe the motion of the colliding objects. They design their own collisions, trying to change just one condition at a time.

**Big Idea:** Friction is a force (a pull) that slows down
moving objects.

Children study friction by sliding pennies on a variety of surfaces and comparing how far the pennies travel before they stop. Through their explorations, they learn that friction is a force that is always present (though often overlooked) and that different surfaces exhibit different amounts of friction. A common misconception, that moving objects slow down on their own, is also addressed in this lesson.

**Big Idea:** Friction is a force (a pull) that slows down
moving objects.

Children continue to investigate friction as they test the amount of traction created by various kinds of shoes. They discover that the degree of traction shoes supply depends on the materials, textures, and tread patterns of the shoes’ soles: there is more traction when there is more friction between the shoe and the surface it is sliding on. They also realize that, although friction is sometimes a nuisance because it slows things down, at other times we rely on friction for just that reason.

**Big Idea:** On Earth, gravity is a force that pulls everything
down all the time.

Children observe and describe the effects of gravity on their bodies and on falling objects and begin to think about the relationship between weight and the pull of gravity. They draw pictures of what the classroom would look like without gravity to help them realize how universal gravity really is. They also participate in a science talk in which they consider whether gravity is a force.

**Big Idea:** On Earth, gravity is a force that pulls everything
down all the time.

Children drop marbles of different weights to further explore the effects of gravity. They observe that marbles dropped at the same time always land at the same moment, no matter how much the marbles weigh. The children also see that the heaviest marbles make the biggest holes.

**Big Idea:** Motion is movement. You can describe an object’s
motion by how long it takes, how far the object travels, how fast the object
goes, and what path it follows. The way to change how something moves is to give
it a push or a pull.

Children review important concepts from the Motion Unit as they slide, jump, and experiment with colliding balls. They try to give detailed descriptions of each of the motions used in these activities and consider some of the pushes and pulls (forces) involved. This fun, action-packed lesson can be taught outdoors on the playground or indoors in the gymnasium or another suitable open space.

**Big Idea:** Observation is a powerful tool for learning about
something. Detailed and accurate descriptions of your observations help you
communicate them to others.

Children practice making accurate and detailed descriptions before and after observing a familiar object. In doing so, they discover the importance of careful observation and detailed description in science.

**Big Idea:** Measuring how much something weighs is a basic
scientific skill.

Children compare the weight of various objects using balances and scales. They gain an appreciation and awareness of weight, and strengthen their measuring skills.