KINEMATICS

IB Physics > Mechanics
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 * KINEMATICS || FORCES AND DYNAMICS || WORK, ENERGY AND POWER || UNIFORM CIRCULAR MOTION ||

KINEMATICS
I'm not sure if it will load in China! media type="custom" key="8758830" 2.1.1 Define //displacement//, //velocity//, //speed// and //acceleration//. Quantities should be identified as scalar or vector quantities. See sub-topic 1.3.
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VELOCITY: The rate of change of displacement with time. A vector. Unit: ms -1

DISPLACEMENT: The distance travelled in a particular direction from a specified origin. A vector. SPEED AND DISTANCE: The scalar versions of velocity and displacement. ACCELERATION: The rate of change of velocity with time. A vector. Unit ms -2

2.1.2 Explain the difference between instantaneous and average values of speed, velocity and acceleration. INSTANTANEOUS: The value of a quantity measured at an instant in time, as opposed to an average quantity measured over a period of time. 2.1.3 Outline the conditions under which the equations for uniformly accelerated motion may be applied.

EQUATIONS OF UNIFORMLY ACCELERATED MOTION: Equations relating five quantities, u, v, a, s, t. Each equation contains 4 of the variables. 2.1.4 Identify the acceleration of a body falling in a vacuum near the Earth’s surface with the acceleration //g// of free fall. ACCELERATION DUE TO GRAVITY: Ignoring air resistance, a free-falling object accelerates at the surface of the Earth at approx. 9.8ms -2 This is numerically equal to gravitational field strength. 2.1.5 Solve problems involving the equations of uniformly accelerated motion.

2.1.6 Describe the effects of air resistance on falling objects. Only qualitative descriptions are expected. Students should understand what is meant by terminal speed. TERMINAL VELOCITY: Air resistance is proportional to speed, so an accelerating object will achieve terminal velocity. ** media type="custom" key="12412094" 2.1.7 Draw and analyse distance–time graphs, displacement–time graphs, velocity–time graphs and acceleration–time graphs. Students should be able to sketch and label these graphs for various situations. They should also be able to write represented by such graphs.
 * MAN JUMPS FROM SPACE

2.1.8 Calculate and interpret the gradients of displacement–time graphs and velocity–time graphs, and the areas under velocity–time graphs and acceleration–time graphs.

ACTIVITY: For each of the graphs below, calculate displacement, velocity and acceleration for each stage, where possible. [|Graphs of motion for practice calculation.pdf] DISPLACEMENT-TIME GRAPHS: Gradient is velocity. VELOCITY-TIME GRAPHS: Gradient is acceleration. Area under graph is displacement. ACCELERATION-TIME GRAPHS: Area under graph is change in velocity. ACTIVITY: For each of the graphs above, calculate displacement, velocity and acceleration for each stage, where possible.

2.1.9 Determine relative velocity in one and in two dimensions. RELATIVE VELOCITY: A velocity measured from the point of view of another moving object (eg the velocity of a car with respect to the bicycle it passes).


 * Velocity of A as seen from B (V AB) = V A - V B ** (also known as **velocity of A //relative// //to// B**)

EXAMPLE 1: A car travelling north at 20 m/s passes a van travelling south at 15 m/s. What is the velocity of the car as seen from the van? EXAMPLE 2: An athlete running due east at 7 m/s sees a bicycle travelling at 10 m/s due south. What is the velocity of the bicycle relative to the van? EXAMPLE 3: A bug crawls at 5 cm/s north on a twig which is floating on a river flowing 20 cm/s west. What is the bug's velocity relative to a) the twig; b) the water; c) the river bank?

PRACTICE QUESTIONS FROM GIANCOLI BOOK [|giancoli acceleration questions.pdf] [|giancoli motion graphs.pdf] [|giancoli relative velocity.pdf]

USEFUL FILES [|Equations of uniformly accelerated motion.doc] [|Graphs of motion - IB notes] [|IB Mechanics notation.doc]