Newton's Laws of Motion

Question 1

What is a force?

Answer 1

A force is a push or pull.

Because forces have both magnitude (size) and direction, they are known as vector quantities.

Force is measured in Newtons.

Question 2

What are External Forces?

Answer 2

External Forces are forces that originate outside the object or body that we wish to study (gravity).

Question 3

What are Internal Forces?

Answer 3

Internal Forces arise within the system that we are interested in studying (muscle contraction).

Question 4

What is Newton’s first law?

Answer 4

The Law of Inertia.

A body or object either remains in a stationary position or continues to move at a constant velocity, unless an external force is exerted upon it.

Inertia is the property of matter that causes an object to resist any changes in motion.

Question 5

What is the second law?

Answer 5

The Law of Acceleration.

F=ma (F is force, m is mass, a is acceleration).

‘A force applied to an object causes an acceleration of that object of a magnitude proportional to the force and in the direction of the force, but inversely proportional to the object’s mass.’

Question 6

What is the third law?

Answer 6

The law of action/reaction.

‘A reaction force arises whenever one body exerts a force on another. The reaction force is equal and opposite in magnitude and direction to the applied force.’

Example:

When a basketball player jumps to make a slam dunk. The action of pushing against the court floor leads to a reaction force—that is, the floor pushing back—and, ultimately, the athlete’s body leaves
the ground.