Y3 Y4 ACSI IP Physics Chapter 2

CORE NOTES CHAPTER 2: KINEMATICS By: Oscar Chiang Page 1 - Terms Scalar quantities are physical quantities that have magnitude only. Vector quantities are physical quantities that have both magnitude and direction. Kinematics Equations ① 𝑣 = 𝑢 + 𝑎𝑡 ② 𝑣# = 𝑢# + 2𝑎𝑠 ③ 𝑠 = 𝑢𝑡 + %#𝑎𝑡# where 𝑣 = final velocity, 𝑢 = initial velocity, 𝑎 = acceleration, 𝑡 = time, 𝑠 = displacement. - Part I: Physical Quantities where 𝑑 = distance, 𝑡 = time taken, 𝑠 = displacement, 𝑣 = final velocity, 𝑢 = initial velocity. - Part II: Graphs of Motion Type of Graph Area Gradient Distance-time graph Distance covered Speed Displacement-time graph Displacement covered Velocity Speed-time graph Distance covered Acceleration Velocity-time graph Displacement covered Acceleration-time graph Average velocity Quantities Definition SI Unit Type of quantity Formula Distance Distance is the total length covered by an object, regardless of its direction of motion. metre (𝑚) Scalar Displacement Displacement is the change of position of an object. Vector Speed Speed is the distance moved per unit time. metre per second (𝑚𝑠&%) Scalar 𝑑𝑡 Velocity Velocity is the rate of change of displacement. Vector 𝑠𝑡 Acceleration Acceleration is the rate of change of velocity. metre per second squared (𝑚𝑠&#) Vector 𝑣−𝑢𝑡 No air resistance

By: Oscar Chiang Page 2 - Part III: Acceleration • Acceleration with no air resistance (free fall) When an object is moving up (against gravity) or moving down in free fall, the acceleration is −10𝑚𝑠&#. Acceleration due to gravity = −𝟏𝟎𝒎𝒔&𝟐 Therefore, regardless of mass, when air resistance is not considered, all objects will fall at the same acceleration due to Earth’s gravity. Tip: Even if acceleration applies to an entire system of objects, it applies to a single object individually as well. • Acceleration with air resistance Air resistance is a frictional force and will… a. always oppose the motion of moving objects. b. increases with the speed of the objects. c. increases with surface area of the objects. d. increases with density of air. - Part IV: Terminal Velocity When objects’ air resistance increases with the object’s speed, when the air resistance is equal to the weight of the object, the object has reached its terminal velocity. Hence, it travels at a constant speed with zero acceleration. Terminal velocity is when the object is no longer accelerating and moving at a constant velocity. Terminal velocity occurs when the upward force and downward force is equal in a free fall. • Factors affecting Terminal Velocity 1. Weight The heavier an object is, the longer it will take to reach its terminal velocity and will have greater terminal velocity. 2. Surface Area The smaller the surface area of an object is, the longer it will take to reach its terminal velocity and will have greater terminal velocity. - Part VI: Type of Graph Gradients Positive Gradient Linear (constant) increase Increasing gradient Decreasing gradient At rest Negative gradient Linear (constant) increase Increasing gradient Decreasing gradient At rest Note! Deceleration is used when the speed of an object reduces. When acceleration is negative, it is said to be accelerating in the negative direction!