IGCSE EXAMS TIPS

IGCSE Physics: Chapter on Motion – Key Notes

1. Distance and Displacement

• Distance: The total path length covered by an object, regardless of direction (scalar quantity).

• Displacement: The shortest straight-line distance from the initial to the final position of an object, including direction (vector quantity).

• Formula for Displacement: Displacement=Final Position−Initial Position\text{Displacement} = \text{Final Position} - \text{Initial Position}

2. Speed and Velocity

• Speed: The rate of change of distance (scalar quantity).

  
  

  Formula: Speed=DistanceTime\text{Speed} = \frac{\text{Distance}}{\text{Time}}

• Velocity: The rate of change of displacement (vector quantity).

  
  

  Formula: Velocity=DisplacementTime\text{Velocity} = \frac{\text{Displacement}}{\text{Time}}

• Units: Speed and velocity are measured in meters per second (m/s).

3. Acceleration

• Acceleration: The rate of change of velocity (vector quantity).

  
  

  Formula: Acceleration=Change in VelocityTime taken\text{Acceleration} = \frac{\text{Change in Velocity}}{\text{Time taken}}

• Positive acceleration is an increase in velocity, while negative acceleration (deceleration) is a decrease in velocity.

4. Equations of Motion

These equations describe the relationship between velocity, acceleration, displacement, and time. They are valid for uniform acceleration (constant acceleration).

• First equation of motion:

  v=u+atv = u + at

  where:

  • vv = final velocity

  • uu = initial velocity

  • aa = acceleration

  • tt = time

• Second equation of motion:

  s=ut+12at2s = ut + \frac{1}{2} a t^2

  where:

  • ss = displacement

  • uu = initial velocity

  • aa = acceleration

  • tt = time

• Third equation of motion:

  v2=u2+2asv^2 = u^2 + 2as

  where:

  • vv = final velocity

  • uu = initial velocity

  • aa = acceleration

  • ss = displacement

5. Graphical Representation of Motion

• Distance-time graph:

  • A straight line indicates uniform motion (constant speed).

  • A curved line indicates changing speed (accelerating or decelerating).

• Velocity-time graph:

  • A straight, horizontal line indicates constant velocity (no acceleration).

  • The slope of the graph indicates acceleration.

  • The area under the graph represents displacement.

6. Uniform Circular Motion

• Motion of an object traveling at a constant speed in a circular path.

• The object constantly accelerates because its direction is changing, even though its speed is constant. This acceleration is called centripetal acceleration.

• Centripetal acceleration formula: ac=v2ra_c = \frac{v^2}{r} where:

  • vv = speed of the object

  • rr = radius of the circular path

7. Relative Velocity

• The velocity of one object as observed from another object.

• Formula: Relative Velocity=vobserver−vobject\text{Relative Velocity} = v_{\text{observer}} - v_{\text{object}}

• For two objects moving in the same direction: vrelative=v1−v2v_{\text{relative}} = v_1 - v_2

• For two objects moving in opposite directions: vrelative=v1+v2v_{\text{relative}} = v_1 + v_2

8. Projectile Motion

• Motion of an object thrown at an angle to the horizontal. The object moves under the influence of gravity.

• The motion has two components: horizontal motion (constant velocity) and vertical motion (accelerated due to gravity).

• Horizontal displacement (range): R=v02sin⁡(2θ)gR = \frac{v_0^2 \sin(2\theta)}{g} where:

  • v0v_0 = initial velocity

  • θ\theta = angle of projection

  • gg = acceleration due to gravity

9. Important Terms

• Instantaneous Speed: The speed of an object at any particular moment in time.

• Instantaneous Velocity: The velocity of an object at a particular point in time, considering direction.

• Average Speed: The total distance traveled divided by the total time taken.

• Average Velocity: The total displacement divided by the total time taken.

10. Units in Motion

• Distance: Meter (m)

• Time: Second (s)

• Speed/Velocity: Meters per second (m/s)

• Acceleration: Meters per second squared (m/s²)

• Force (when applicable): Newton (N)

• Mass: Kilogram (kg)

These are the core concepts of motion in IGCSE Physics. Understanding the equations of motion, their graphical interpretations, and various types of motion such as projectile and circular motion are key to mastering this chapter.