Nature of Force and Its Effects
- Jun 11
- 1 min read
What is a Force?
Force is a push or a pull acting on an object.
A force is needed to start, stop, speed up, slow down, or change the direction of motion of an object.
Unit of Force is Newton (N).
A force always has:
Magnitude
Direction
Therefore, force is a vector quantity because it has both magnitude and direction.
Newton's Laws of Motion and Force
Newton's First Law
"An object remains at rest or continues to move with uniform velocity unless acted upon by an
unbalanced force."
Examples:
A stationary football remains at rest until kicked.
Passengers move forward when a moving bus suddenly stops.
Key Point:
Force is needed to change the state of motion.
Newton's Second Law
"The acceleration of an object is directly proportional to the force applied and inversely proportional to its mass."
Relationship:
F = ma
Where:
F is the Force (N)
m is the Mass (kg)
a is the Acceleration (m s⁻²)
What is the force required to give an acceleration of 2 m s⁻², to a 5kg mass ?
F = ma
= 5 kg × 2 m s⁻²
= 10 N
Simple Idea:
Greater force → Greater acceleration
Greater mass → Smaller acceleration
Example:
It is easier to push an empty trolley than a loaded trolley.
Newton's Third Law
"For every action, there is an equal and opposite reaction."
Simple Idea:
Forces always occur in pairs.
Examples:
A rocket moves upward because gases are pushed downward.
A swimmer pushes water backward and moves forward.
Key Point:
Action force and reaction force:
Are equal in magnitude.Act in opposite directions. Act on different objects.
