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Vector quantity, Meaning (SPM Physics)

A physical quantity that has both magnitude and direction, such as displacement, velocity and force.

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EnglishVector quantity
Bahasa MelayuKuantiti vektor
中文矢量

Definition

A physical quantity that has both magnitude and direction, such as displacement, velocity and force.

Measurement

In exam terms

A vector quantity is a physical quantity that has both magnitude and direction. To describe it fully you must state how much and which way.

Examples in SPM include displacement, velocity, acceleration, force, momentum and weight. Vectors are drawn as arrows: the length shows magnitude and the arrowhead shows direction.

They are added using the triangle or parallelogram method, not simple arithmetic. A correct sentence: Velocity is a vector quantity of 20 m s⁻¹ to the north.

Do not confuse it with scalar quantity

Do not confuse a vector with a scalar quantity, which has magnitude only. Two forces of 3 N and 4 N do not always give 7 N: if they act at right angles the resultant is 5 N, found using the parallelogram method.

In Paper 2, a question may ask you to determine the resultant of two vectors or to state why a quantity is a vector. Always mention direction in the reason, and show the arrow diagram when adding vectors.

Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)

Frequently asked questions

Why is displacement a vector but distance is not?
Displacement states how far and in which direction from the start, so it has direction. Distance states only the total path length, with no direction, so it is a scalar.
Can two equal forces give a zero resultant?
Yes. If two forces of the same magnitude act in exactly opposite directions, the resultant is zero because the directions cancel.
How do I add two vectors at an angle?
Use the parallelogram or triangle method. For 3 N and 4 N at right angles, the resultant is the diagonal, of magnitude 5 N by Pythagoras.

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