Acceleration & Velocity-Time Graphs & Newton's Laws

What is acceleration?

The rate of change of velocity.

What is deceleration?

Acceleration that reduces an object's speed.

What is the unit of acceleration?

m/s².

What does the gradient of a velocity–time graph represent?

Acceleration.

What does a horizontal line on a velocity–time graph mean?

Constant velocity.

What does a straight line with a positive gradient mean?

Constant positive acceleration.

What does a negative gradient mean?

Negative acceleration.

What does the area under a velocity–time graph represent?

Displacement, taking account of positive and negative areas.

When does the area under a velocity–time graph equal distance travelled?

When velocity does not change sign, so the object does not reverse direction.

How can acceleration be found at a point on a curved velocity–time graph?

Draw a tangent and determine its gradient.

State Newton's First Law.

If the resultant force is zero, a stationary object remains stationary and a moving object continues at constant velocity.

What happens to an object moving at constant velocity if the resultant force is zero?

It continues moving at the same speed in the same direction.

Does a moving object always require a resultant force to keep moving?

No, a resultant force is needed to change velocity, not maintain constant velocity.

Why does a car travelling at constant speed on a straight road have zero resultant force?

The driving force balances the resistive forces.

What is inertia?

The tendency of an object to remain at rest or continue moving at constant velocity unless acted on by a resultant force.

State Newton's Second Law.

Acceleration is directly proportional to resultant force and inversely proportional to mass.

What is inertial mass?

A measure of how difficult it is to change an object's velocity.