Exam Notes - Essential Physics Concepts

Movement and Position

• Average Speed: Calculated as $v = \frac{s}{t}$, where $v$ is average speed, $s$ is distance moved, and $t$ is time taken.

• Units of Speed: Commonly measured in meters per second (m/s).

• Distance-Time Graphs:

  • A straight line indicates constant speed.

  • The slope (gradient) of the line represents speed.

  • A curved line indicates changing speed.

• Velocity: Speed in a specific direction; a vector quantity.

• Average Velocity: Calculated as $\text{average velocity} = \frac{\text{increase in displacement}}{\text{time taken}}$

Acceleration

• Definition: The rate at which an object changes its velocity.

• Formula: $a = \frac{v - u}{t}$, where $a$ is acceleration, $v$ is final velocity, $u$ is initial velocity, and $t$ is time taken.

• Units: Measured in meters per second squared (m/s²).

• Deceleration: Negative acceleration, indicating slowing down.

• Velocity-Time Graphs:

  • The gradient represents acceleration.

  • The area under the graph represents the distance traveled.

Forces and Shape

• Forces: Pushes or pulls that can change an object's speed, shape, or direction.

• Types of Forces: Gravitational, electrostatic, friction, etc.

• Vector vs. Scalar Quantities: Force is a vector (magnitude and direction), while temperature is a scalar (magnitude only).

• Resultant Force: The net force acting on an object, considering direction.

• Friction: A force that opposes motion.

• Hooke’s Law: The extension of a spring is proportional to the applied force, within its elastic limit.

Forces and Movement

• Newton's Second Law: $F = m \times a$, where $F$ is unbalanced force, $m$ is mass, and $a$ is acceleration.

• Weight: The force of gravity on an object, calculated as $W = m \times g$, where $g$ is gravitational field strength.

• Stopping Distance: The sum of thinking distance and braking distance.

• Factors Affecting Stopping Distance: Speed, mass, road condition, and reaction time.

• Air Resistance and Terminal Velocity: As an object falls, air resistance increases until it equals the weight, resulting in terminal velocity.

Momentum (Physics Only)

• Definition: A measure of how difficult it is to stop a moving object.

• Formula: $p = m \times v$, where $p$ is momentum, $m$ is mass, and $v$ is velocity.

• Units: Kilogram meters per second (kg m/s).

• Newton's Second Law (Momentum Form): $F = \frac{mv - mu}{t}$, where $F$ is force, $m$ is mass, $v$ is final velocity, $u$ is initial velocity, and $t$ is time.

• Conservation of Momentum: In a closed system, the total momentum before a collision equals the total momentum after the collision.

• Newton's Third Law: For every action, there is an equal and opposite reaction.

Turning Effect of Forces (Physics Only)

• Moment of a Force: $\text{moment} = \text{force} \times \text{perpendicular distance from the pivot}$

• Balance occurs when $\text{sum of anticlockwise moments} = \text{sum of clockwise moments}$.