9702 · 2.1
Equations of motion — FAQ
Frequently asked questions for 9702 Equations of motion. Direct answers first, then deeper explanation — then practise with marking.
What is the difference between speed and velocity in physics?
Speed is a scalar quantity that only describes how fast an object is moving (its magnitude). Velocity is a vector quantity that describes both how fast an object is moving and in what direction. For example, '30 m/s' is a speed, while '30 m/s East' is a velocity.
When can I use the SUVAT equations?
You can use the SUVAT equations only when an object is moving with uniform (constant) acceleration in a straight line. They are not applicable if the acceleration is changing or if the motion is not linear (e.g., circular motion).
How do I deal with negative values for displacement, velocity, or acceleration?
Negative values indicate that the quantity is in the opposite direction to the one you defined as positive. For example, if 'upwards' is positive, a negative displacement means the object is below its starting point, and a negative velocity means it's moving downwards.