Browse Lessons
Assign Lesson

Help Teaching subscribers can assign lessons to their students to review online!

Assign Lesson to Students

Share/Like This Page

Force and Motion

Force and Motion

This lesson aligns with NGSS PS2.A

Introduction
The fundamental factor influencing the movement of an object is identified as force. Similarly, the moving object is also attributed to force. Therefore, force and motion can be interconnected just like the two sides of a coin. An illustrative example of the interdependence of force and motion is evident in actions like throwing a ball and subsequently catching it. To gain a comprehensive understanding, it is essential to first grasp the individual meanings of force and motion before delving into the relationship that binds them together. In this article, we delve into the concept of force and motion, exploring their definitions, principles, and providing real-world examples to illustrate their applications.

What is Force?
Force can be defined as the action of pushing or pulling exerted on an object. Such interactions typically manifest when two entities come into contact.
Additionally, according to the universal law of gravitation, every object within the universe exerts a force on other objects.
It is a vector quantity, which means it has both magnitude and direction. Force is measured in Newtons (N) in the International System of Units (SI).

Principles of Force

Newton's First Law of Motion
Newton's first law, often referred to as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue to move with a constant velocity unless acted upon by a net external force. In simpler terms, objects resist changes in their state of motion.

Newton's Second Law of Motion
Newton's second law relates the force applied to an object, its mass, and its resulting acceleration. The formula is expressed as
     F=ma 
where
  • F is the force applied,
  • m is the mass of the object, and
  • a is the acceleration produced.

Newton's Third Law of Motion
Newton's third law asserts that for every action, there is an equal and opposite reaction. When one object exerts a force on a second object, the second object simultaneously exerts a force of the same magnitude but in the opposite direction on the first object.

Motion
When a body is in a state of movement, we describe it as being in motion. For example, if a boy is walking along the street from his school to his home, we characterize him as being in motion. However, consider a scenario where the boy stops for 5 minutes on his way and sits down. If queried during this pause whether the boy is in motion, the response would be 'No.' This implies that the motion of a body is dependent upon time.

Principles of Motion
Distance and Displacement:
Distance refers to the total path length travelled, while displacement is the change in position of an object in a particular direction. Displacement involves both distance and direction.

Speed and Velocity:
Speed is the rate at which an object covers distance, expressed as the distance travelled per unit of time. Velocity, on the other hand, is the rate of change of displacement, encompassing both speed and direction.

Acceleration:
Acceleration is the rate at which an object changes its velocity. It is calculated as the change in velocity per unit of time and can be influenced by the application of force.

Force and Motion
Force can cause a body to accelerate
Applying force to an object at rest induces movement, assuming there is no opposing force of greater magnitude. For instance, in cricket when you throw a ball towards the batsman. The ball starts its motion from a state of rest in your hands.
As an object transitions from a state of rest, it undergoes acceleration, defined as a positive alteration in velocity within a specific timeframe.
Likewise, when force is exerted in the same direction as the movement of an already moving object, it experiences acceleration. An exemplification of this principle is observable when you rotate the pedal of a bicycle, causing it to accelerate and move at an increased speed.

Force can cause a body to decelerate
Conversely, when force is exerted in the opposite direction of a moving object, the object undergoes deceleration, leading to a decrease in speed and eventually stops if the force persists. For example, when a goalkeeper stops a ball, resulting in the ball decelerating and eventually coming to a stop.

Force can cause a body to change directions
When force is applied to an object at an angle divergent from its current direction of motion, it causes a change in the object's trajectory. This principle finds widespread application in various ball games. The object's speed can be sustained if the force is applied at a right angle, but it results in a change in velocity.

Summary
  • Force can be defined as the action of pushing or pulling exerted on an object.
  • When a body is in a state of movement, we describe it as being in motion. For example, if a boy is walking along the street from his school to his home, we characterize him as being in motion.
  • Distance refers to the total path length traveled, while displacement is the change in position of an object in a particular direction.
  • Acceleration is the rate at which an object changes its velocity.

Related Worksheets:

Become a Help Teaching Pro subscriber to access premium lessons

Unlimited premium lessons Unlimited premium printables Unlimited online testing

Learn More About Benefits and Options