Force and Motion

Front

Motion Noun

---

[moh-shun]

Back

Motion

---

A change in an object's position over time when compared to a fixed reference point or another object.

---

Example: This image lists text examples of motion, such as running and walking, but does not visually show or explain what motion is.

Front

Reference Frame Noun

---

[ref-er-uhns freym]

Back

Reference Frame

---

A coordinate system or a set of axes used for comparison to determine if an object is in motion.

---

Example: The measurement of an object's motion depends on the observer's reference frame. Here, the ball's speed relative to the earth is the sum of its speed on the moving walkway.

Front

Reference Point Noun

---

[ref-er-uhns point]

Back

Reference Point

---

A specific, fixed location or object used as a basis for comparison to determine the position of another object.

---

Example: A compass provides fixed directions (North, South, East, West) that can be used as a reference point to describe an object's location or motion.

Front

Displacement Noun

---

[dis-pleys-muhnt]

Back

Displacement

---

The shortest distance and direction from an object's starting point to its ending point, representing a change in position.

---

Example: This image shows a teacher moving from an initial position (x₀) to a final position (xf). Displacement is the change in position, calculated as the final position minus the initial position.

Front

Speed Noun

---

[speed]

Back

Speed

---

The rate at which an object covers distance, calculated as the distance an object travels per unit of time.

---

Example: This image shows that speed is calculated by dividing the distance an object travels by the time it takes to travel that distance.

Front

Velocity Noun

---

[vuh-los-i-tee]

Back

Velocity

---

The rate of change of an object's position, which includes both its speed and its specific direction of motion.

---

Example: This diagram shows the formula for velocity (v) as displacement (d) divided by time (t), using a triangle to help remember the relationship.

Front

Force Noun

---

[fors]

Back

Force

---

An interaction, such as a push or a pull, that can change the motion of an object and has strength and direction.

---

Example: A force is a push or a pull on an object. This image shows a boy applying a push force and a pull force to a crate.

Front

Newton (N) Noun

---

[noo-tn]

Back

Newton (N)

---

The standard international (SI) unit of force, used to measure the strength or magnitude of a push or pull.

---

Example: This icon shows a person applying a force (a push) to an object, with an arrow indicating the force's direction.

Front

Contact Force Noun

---

[kon-takt fors]

Back

Contact Force

---

A force that acts on an object by direct physical touch, requiring the interacting objects to be in contact.

---

Example: This image shows three examples of contact forces: friction slowing a sled, a spring pushing a toy, and muscles lifting a weight, all requiring physical touch.

Front

Noncontact Force Noun

---

[non-kon-takt fors]

Back

Noncontact Force

---

A force that is applied to an object by another body that is not in direct contact with it.

---

Example: This diagram shows two bar magnets attracting each other without touching, demonstrating magnetism as a type of noncontact force.