Free Body Diagrams

What does a free body diagram show?

The direction and magnitude of all the forces acting on an object.

What is a vector?

A quantity that has both magnitude and direction.

What is weight?

The force experienced by mass due to gravity.

What direction does weight always act on a free body diagram?

Downwards (towards the Earth).

What is the normal contact force?

The force that stops an object moving through a surface; it acts at right angles to the surface.

What direction does the normal contact force act?

Upwards, away from the surface.

How does the normal contact force compare in magnitude to the total downward force?

It is equal in magnitude.

What does the driving force do?

Does work to convert chemical energy to kinetic energy (propels the object forward).

What direction does the driving force act?

Forwards.

What direction do friction and drag act relative to the object's motion?

Opposite to the direction of motion.

What causes friction and drag?

Resistance to motion due to collisions with air particles and surfaces sliding past each other that aren't completely smooth.

What is the resultant force?

The overall effect of all forces on the object.

In the car example, why do weight and normal contact force cancel each other out?

They have the same magnitude but opposite directions (balanced forces).

In the car example, why is the resultant force to the right?

Because the driving force to the right is larger than the friction which opposes it (vertical forces are balanced).

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