Contact and Non-Contact Forces

Front

Force Noun

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[forss]

Back

Force

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A push or a pull on an object resulting from its interaction with another object, causing a change in motion.

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Example: A person pushing an object demonstrates a contact force, where the push is the force being applied in the direction shown by the arrow.

Front

Newton Noun

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[noo-tn]

Back

Newton

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The standard international (SI) unit used to measure the magnitude of a force, symbolized as N.

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Example: This image shows Isaac Newton realizing that the same non-contact force, gravity, that pulls an apple to the ground also acts on other objects.

Front

Contact Force Noun

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[kon-takt forss]

Back

Contact Force

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

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Example: This image shows a boy pushing and pulling a crate, demonstrating that a contact force is applied when objects are physically touching.

Front

Applied Force Noun

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[uh-plahyd forss]

Back

Applied Force

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A force that is directly applied to an object by another object or a person to cause a change in motion.

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Example: A person applies an upward contact force to hold a box against gravity. This shows the direction of the applied force can be different from the direction of motion.

Front

Muscular Force Noun

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[muhs-kyuh-ler forss]

Back

Muscular Force

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A contact force generated by the contraction of muscles in the body to produce movement or maintain position.

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Example: Two people use their muscles to pull on a rope, applying a muscular force in opposite directions, which is a type of contact force.

Front

Friction Noun

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[frik-shuhn]

Back

Friction

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A contact force that opposes the relative motion or tendency of motion between two surfaces that are in contact.

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Example: This diagram shows a car moving along a surface, illustrating that friction is a contact force that opposes the direction of motion.

Front

Air Resistance Noun

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[air ri-zis-tuhns]

Back

Air Resistance

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A type of frictional force that acts upon objects as they travel through the air, opposing their motion.

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Example: This diagram shows the four main forces on a flying paper plane, identifying drag as the specific force of air resistance that opposes motion.

Front

Normal Force Noun

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[nor-muhl forss]

Back

Normal Force

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The support force exerted by a surface upon an object in contact with it, acting perpendicular to the surface.

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Example: When a book rests on a table, the table exerts an upward contact force, called the normal force, that balances the downward pull of gravity.

Front

Tension Force Noun

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[ten-shuhn forss]

Back

Tension Force

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The pulling force transmitted axially through a string, rope, or cable when pulled by opposing forces from opposite ends.

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Example: Two people pulling on a rope create a tension force, which is the pulling force transmitted through the rope when it is pulled taut.

Front

Spring Force Noun

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[spring forss]

Back

Spring Force

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The force exerted by a compressed or stretched spring upon any object that is attached to it.

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Example: A spring creates a restoring force when it is stretched or compressed, trying to return to its original 'natural length'.