IB Physics: Kinematics Kinematics Define displacement, velocity, speed and acceleration The distance an object travels in a specific direction is known as displacement. ● Unit: Metre ( m ) ● Scalar quantiy Velocity : The displacement per unit time ● Unit: Metres per Second ( m/s ) ● Vector quantity ● Equation: Displacement/Time Speed : The distance travelled per unit time ● Unit: Metres per Second ( m/s ) ● Scalar quantity ● Equation: Distance/Time Acceleration : The rate of change of velocity ● Unit: Metres per Second Squared ( m/s-2 ) ● Vector quantity ● Equation: Change in Velocity/Time Explain the difference between instantaneous and average values of speed, velocity and acceleration Instantaneous Velocity : The velocity of an object at a certain point in time and the direction its travelling in Average Velocity : The average of the given values of velocity ● Remember that Velocity is relative meaning that the Velocity of an object is dependent onthe obeserver for example, the speed of a bus will appear faster to someone standing stillcompared to someone walking. Equation for Average Velocity: (Initial Velocity+Final Velocity)/Time Equation for Instantaneous Velocity: Velocity Initial + (Acceleration* Time) Outline the conditions under which the equations for uniformly accelerated motion may be applied In one-dimensional motion, the acceleration, velocity and displacement are all in the same direction. Due to this we can deduce these equations: A= Acceleration S= Displacement V= Final Velocity
U= Initial Velocity T= Time A= (V-U)/T S= (U+V)T/2 S= UT+1/2AT^2 V^2= U^2+2AS Determine relative velocity in one and in two dimensions These are called the suvat equations and they all require acceleration in order to be used. Not only do these equations require acceleration but also because these equations are used in one dimension, velocity, displacement and acceleration can have a positive or negative value which indicates which direction they’re going in. This is mainly dependent on the question though but we can assume that positive velocity and displacement means the object is going right as the object can only go left or right. Acceleration is a bit more different since the acceleration can be positive even if the object is moving right or left. Identify the acceleration of a body falling in a vacuum near the Earth’s motion Occasionally in a question, you’ll be asked to use one of the suvat equations to find a variable for a body free falling. You will realize acceleration is not given since the acceleration of a free fallingobject is 9.81ms^-2. This is because the acceleration of a free falling body is dependent on the gravity of Earth therefore its 9.81ms^-2.