What does a spring balance measure

The spring balance provides a mass measurement

mass

Explanation:

The mass is hung on the end of a spring, and the deflection of the spring due to the downwards gravitational force on the mass is measured against a scale.

c because the action was the roller coaster reaches bottom of hill (action) reaction would be blood tends to drain away from head

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current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete