The Earth pulls down on a diver falling toward the pool.
Newton's third law promises a second force, the other side of that interaction: the partner force. Which force is it?
There is a mechanical way to name it, every time.
A force sentence names two objects: the object exerting the force, and the object the force acts on. In 'the Earth pulls down on the diver', the Earth is the exerter and the diver is the acted-on object.
To name the partner force, swap the two roles. The acted-on object becomes the exerter, and the exerter becomes the acted-on object.
The direction reverses. The magnitude stays equal. The type stays the same.
So the partner of 'the Earth pulls down on the diver' is 'the diver pulls up on the Earth'.
The partner always comes from the same interaction, the same two objects. The water's upward force on the diver is not the partner of the Earth's downward force on her: it belongs to a different interaction, the diver and the water.
The frame for every answer: the acted-on object exerts a force on the old exerter, equal in magnitude, opposite in direction, same type.
A rowboat's oar exerts a backward force on the water. Name the partner force.
Name the two objects: the oar (exerter) and the water (acted on).
Swap the roles: the water becomes the exerter, the oar the acted-on object.
Reverse the direction: backward becomes forward.
Keep the magnitude equal and the type the same.
The water exerts a forward force on the oar, equal in magnitude.
The Earth exerts a 600 N downward gravitational force on a hang glider. Name the partner force.
Name the two objects: the Earth (exerter) and the glider (acted on).
Swap the roles and reverse the direction.
Keep the magnitude and the type: 600 N, gravitational.
The glider exerts a 600 N upward gravitational force on the Earth.
A soccer player's foot exerts a forward force on the ball. Which is the partner force?
A swimmer's hand exerts a backward force on the water. Which is the partner force?
The Earth exerts a downward gravitational force on a hawk. Which is the partner force?
A rope exerts an upward tension force on a bucket of water. Which is the partner force?
A magnet exerts a magnetic force on a steel washer, directed toward the magnet. Which is the partner force?
A hockey stick's blade exerts a force on a puck, directed toward the goal. Which is the partner force?
The Earth exerts a 550 N downward gravitational force on Tilda as she rides a zip line. Which is the partner force?
A bookshelf rests on a floor. The floor exerts an upward normal force on the shelf. Which is the partner force?
A climber's hand exerts a 400 N downward force on a climbing hold. Which is the partner force?