Coaching Centre
Chapter 5: Objects in Motion Notes
How things move and why: distance and displacement, vectors, speed and velocity, ticker timers, acceleration and g, position–time and velocity–time graphs, Newton's three laws, F = ma, momentum and collisions, kinetic and potential energy, work and efficiency, and the physics of stopping distances and car safety.
Sections
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5A Distance, displacement and vectors Mastered
Describing position and motion, scalar and vector quantities, the difference between distance and displacement, finding displacement with Pythagoras and bearings, and adding vectors head to tail.
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5B Speed and velocity Mastered
Average and instantaneous speed, converting between km/h and m/s, velocity as speed in a direction, average velocity from displacement, measuring motion with ticker timers, light gates and motion sensors, and analysing ticker tapes.
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5C Acceleration Mastered
Acceleration as the rate of change of velocity, units of m/s², deceleration, calculating acceleration and final velocity, acceleration due to gravity and measuring g, accelerometers, and g-forces.
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5D Motion graphs Mastered
Drawing and interpreting position–time and velocity–time graphs, gradient as velocity and acceleration, area under a velocity–time graph as displacement, and describing a journey from its graphs.
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5E Newton's first law and inertia Mastered
Forces and net force, Newton's first law of motion, inertia and mass, inertia in vehicles and seatbelts, why moving objects seem to stop on their own, circular motion and centripetal force, and the physics of the returning boomerang.
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5F Newton's second law: F = ma Mastered
Newton's second law and the equation F = ma, finding the net force from a force diagram, calculating force, mass and acceleration, mass and weight, investigating acceleration with a trolley and hanging masses, and terminal velocity.
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5G Newton's third law and momentum Mastered
Action–reaction force pairs and Newton's third law, why the pair does not cancel, rockets, walking and recoil, momentum as mass × velocity, conservation of momentum in collisions and explosions, and impulse.
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5H Work and energy in motion Mastered
Kinetic energy and its dependence on speed squared, gravitational and elastic potential energy, work done by a force, the law of conservation of energy, efficiency of bouncing balls, energy transformations in sport, and the woomera as a way of doing more work on a spear.
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5I Road safety and collisions Mastered
Reaction distance, braking distance and stopping distance, what affects them, why braking distance depends on speed squared, the work–energy and impulse explanations of crumple zones, seatbelts and airbags, active safety systems such as ABS, ESC and AEB, and evaluating road safety rules.
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5J Objects in motion review Mastered
A summary of the whole Objects in Motion chapter, every formula with its units, key words, and a mixed test covering displacement and vectors, speed, velocity and acceleration, motion graphs, Newton's three laws, momentum, energy and work, and road safety.