Velocity and Acceleration

Motion

What is speed?

The rate of change of distance.

What is the equation for speed?

Speed = distance ÷ time.

What is the SI unit of speed?

Metres per second (m s⁻¹).

What is velocity?

The rate of change of displacement.

What is the equation for velocity?

Velocity = displacement ÷ time.

What is the SI unit of velocity?

Metres per second (m s⁻¹).

What is displacement?

The distance travelled in a specified direction from the starting point.

What is the difference between distance and displacement?

Distance is a scalar measuring the total path travelled, whereas displacement is a vector measuring the change in position in a particular direction.

What is the difference between speed and velocity?

Speed has magnitude only, whereas velocity has both magnitude and direction.

What is a scalar quantity?

A quantity that has magnitude only.

What is a vector quantity?

A quantity that has both magnitude and direction.

Is speed a scalar or vector quantity?

A scalar quantity.

Is velocity a scalar or vector quantity?

A vector quantity.

Is distance a scalar or vector quantity?

A scalar quantity.

Is displacement a scalar or vector quantity?

A vector quantity.

What does magnitude mean?

The size or numerical value of a quantity.

What does Δ mean in physics?

A change in a quantity.

What does Δs represent?

Change in displacement.

What does Δt represent?

Change in time.

What is average speed?

The speed over a whole journey, calculated by dividing the total distance travelled by the total time taken.

What is the equation for average speed?

Average speed = total distance ÷ total time.

Why can average speed be different from the speed at a particular moment?

An object's speed may change throughout a journey, so average speed combines the faster and slower parts of the journey.

What is instantaneous speed?

The speed of an object at a particular instant in time.

What is acceleration?

The rate of change of velocity.

What is the equation for acceleration?

Acceleration = change in velocity ÷ time taken.

What is the SI unit of acceleration?

Metres per second squared (m s⁻²).

What equation can be used for acceleration using initial and final velocity?

a = (v − u) ÷ t.

What does u represent in the acceleration equation?

Initial velocity.

What does v represent in the acceleration equation?

Final velocity.

What does t represent in the acceleration equation?

Time taken for the velocity to change.

What does Δv represent?

Change in velocity.

Why is acceleration a vector quantity?

Because acceleration has both magnitude and direction.

Can an object accelerate without changing its speed?

Yes. If its direction changes, its velocity changes even if its speed remains constant.

Why does changing direction count as acceleration?

Velocity includes direction, so changing direction causes a change in velocity.

What is deceleration?

A decrease in velocity, which can be represented as negative acceleration.

What does negative acceleration mean?

The acceleration acts in the opposite direction to the chosen positive direction.

Can an object have a high speed but zero acceleration?

Yes. If it moves at constant velocity, its acceleration is zero.

When is acceleration zero?

When velocity remains constant, meaning neither its magnitude nor direction changes.