Forces and Motion
Grade 3 · Science · Study Guide
Learn how pushes, pulls, and gravity make objects move and stop.
A force is a push or a pull. Every time you kick a ball, open a door, or pick up your backpack, you're using force. Forces are what make objects start moving, stop moving, change direction, or change shape.
Gravity is one of the most important forces in nature. It's the force that pulls everything toward Earth's center. That's why a ball you throw always comes back down, and why you stay on the ground instead of floating. The Moon's gravity is about six times weaker than Earth's, which is why astronauts on the Moon bounce when they walk!
Friction is another important force. It acts between two surfaces rubbing together and slows things down. Your shoes grip the floor because of friction. Without friction, you'd slide everywhere! Rough surfaces create more friction, while smooth surfaces create less.
The speed of an object tells us how far it moves in a certain amount of time. When a force acts on an object, it can speed it up, slow it down, or change its direction. A bigger force produces more change in motion than a smaller force. A heavy object needs more force to move than a light one.
Key terms
- force
- A push or pull that can change an object's motion
- gravity
- A force that pulls objects toward each other, keeping us on the ground
- friction
- A force that slows down objects moving against each other
- motion
- A change in the position of an object
- speed
- How fast an object moves — the distance it travels in a given amount of time
Flashcards
- force
- A push or pull that can change an object's speed, direction, or shape
- gravity
- The force that pulls objects toward Earth's center
- friction
- Force that slows objects down by acting between surfaces in contact
- motion
- Change in position of an object over time
- speed
- Distance traveled divided by the time it takes
- air resistance
- Friction caused by air pushing against a moving object
Practice questions
What is a force?
- A type of energy stored in objects
- A push or pull on an object
- The speed of a moving object
- The weight of an object
Show answer
Answer: A push or pull on an object
A force is any push or pull applied to an object. Forces are measured in units called Newtons and can start, stop, or change the direction of motion.
Friction always speeds objects up.
Show answer
Answer: False
Friction always slows objects down or prevents them from sliding. It opposes motion, which is why you need to keep pushing something to keep it moving on a rough surface.
The force that pulls objects toward Earth's center is called ___.
Show answer
Answer: gravity
Gravity is a fundamental force that attracts objects with mass toward each other. Earth's gravity gives everything here weight and keeps the atmosphere around our planet.
Which surface would create the MOST friction?
- Ice
- Wet tile
- Carpet
- Glass
Show answer
Answer: Carpet
Carpet has a rough texture that grabs onto objects, creating high friction. Smooth surfaces like ice and glass have very little friction.
A larger force causes more change in an object's motion than a smaller force.
Show answer
Answer: True
This is one of Newton's key ideas. More force = more change in motion. A hard kick sends a ball farther than a gentle tap.
Fun facts
- On the Moon, you could jump about 6 times higher than on Earth because gravity is weaker there!
- A parachute works by increasing air friction (air resistance) to slow down a falling person.
Get a personalized course on Forces and Motion built around your child.