terminal velocity physics

What is terminal velocity?

• Terminal velocity is the constant maximum velocity reached by a falling object.

• It happens when the resultant force becomes zero.

Memory:
Terminal velocity = constant velocity

What forces act on a falling object?

• Weight acts downwards.

• Air resistance (drag) acts upwards.

• Weight causes the object to accelerate downwards.

• Air resistance opposes the motion.

What happens when an object first starts falling?

• Weight is greater than air resistance.

• There is a downwards resultant force.

• The object accelerates.

What happens as the object speeds up?

• The object moves faster.

• Air resistance increases.

• The resultant force becomes smaller.

• The object continues to accelerate, but at a decreasing rate.

What happens when terminal velocity is reached?

• Air resistance becomes equal to weight.

• Resultant force = 0 N.

• The object stops accelerating.

• It continues falling at a constant velocity.

How does air resistance change during a fall?

At the start:
Air resistance is small.

As speed increases:
Air resistance increases.

At terminal velocity:
Air resistance = weight.

What happens to acceleration during a fall?

• Initially, acceleration is large.

• As air resistance increases, acceleration decreases.

• At terminal velocity, acceleration becomes zero.

What does a velocity-time graph look like for a falling object?

• The graph starts with a steep gradient.

• The gradient gradually decreases as air resistance increases.

• Eventually the graph becomes horizontal.

• The horizontal section represents terminal velocity.

Remember:
Gradient of a velocity-time graph = acceleration

What happens if a parachute opens?

1. The parachute opens → air resistance suddenly increases.

2. Resultant force becomes upwards.

3. The object decelerates.

4. It reaches a new, lower terminal velocity.

Why does a parachutist eventually stop accelerating

• As the parachutist slows down, air resistance decreases.

• Eventually air resistance equals weight again.

• Resultant force = 0 N.

• They fall at a new constant terminal velocity.