A Force Can Change The State Of Motion

key notes:

1. What is Force?

  • Definition: A push or pull on an object caused by interaction with another object.
  • Unit: Newton (N).
  • Types: Contact force (e.g., friction, tension) and non-contact force (e.g., gravitational, magnetic).

2. State of Motion

  • An object’s state of motion refers to whether it is at rest or in motion (constant speed or direction).
  • Rest: Object is stationary.
  • Motion: Object is moving in a specific direction with a specific speed.

3. Effects of Force on the State of Motion

  • Change in Speed: Force can speed up or slow down an object.
  • Change in Direction: Force can change the direction of a moving object.
  • Start or Stop Motion: A stationary object can start moving, or a moving object can stop due to force.
  • Examples:
    • Kicking a football (starts motion).
    • Applying brakes on a bicycle (stops motion).

4. Force and Acceleration

  • When a force is applied to an object, it accelerates according to Newton’s Second Law of Motion:
    F=m⋅a
    where F = Force, m = Mass, and a = Acceleration.

5. Balanced and Unbalanced Forces

  • Balanced Forces: Do not change the state of motion; the object remains at rest or moves with a constant velocity.
  • Unbalanced Forces: Change the state of motion, causing acceleration.

6. Real-Life Examples of Force Changing Motion

  • Pushing a shopping cart: Changes its state from rest to motion.
  • A soccer ball changing direction when kicked by a player.
  • A car accelerating or decelerating when the driver presses the accelerator or brakes.

7. Force and Friction

  • Friction is a force that opposes motion.
  • While applying force, friction must often be overcome to change the motion.

8. Key Points to Remember

  • A net force must act on an object to change its motion.
  • The larger the force applied, the greater the change in motion.
  • Objects resist changes to their state of motion due to inertia (Newton’s First Law of Motion).

9. Activities to Explore

  • Roll a ball on a flat surface and observe its motion. Apply force in different directions and note the changes.
  • Experiment with pushing different weights to feel how force changes the motion differently for objects with varying mass.

Let’s practice!