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Chapter 2: Chapter 2: Forces & MotionForces & Motion

Form 4Form 4

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PhysicsPhysicsNext >

The study of The study of mattermatter

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Objectives: Objectives: ((what you will learnwhat you will learn)) 1) understanding Motion

2) understanding Momentum

3) understanding Forces

Physics: Chapter Physics: Chapter 22

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MotionMotion

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Distance = amount of space between 2 placesDisplacement = distance from a particular pointSpeed = distance traveled per unit of timeSpeed

= distance tim

e , m s-1

Velocity = displacement per unit of timeVelocity =

displacement time , m s-1

Acceleration =

velocitytime

, m s-2

Acceleration = rate of changes in velocity

Deceleration = retardation = negative acceleration

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MotionMotionEquations of motion:v = u + at

v2 = u2 + 2ass = ut + at2

Inertia = tendency of things to resist changes in motionMomentum = mass x velocity

Law of Conservation of Momentum When 2 or more objects act upon each other, their total momentum remains constant; if no external forces are acting.Impulse = changes in momentum = mv mu = FtImpulsive force = rate of change of momentum (in a collision or explosion)

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Newtons LawNewtons LawNewtons First LawEvery object continue in its state of rest or motion in straight line, unless it is compelled to change by forces acting on it.Newtons Second LawThe acceleration of an object is directly proportional to the net force acting on the object, in the direction of the net force, and inversely proportional to its mass.

F = maNewtons Third LawWhenever an object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

21FF11 FF22

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Forces & MotionForces & MotionFree fall = motion under the influence of gravitational pull only. The acceleration of free fall is g.

Earths gravitational field strength (g) is 10 N/kg.

Weight is the force due to gravity on an object. Weight (W) is the product of mass (m) and acceleration due to gravity (g).W = mg

Forces in equilibrium = balanced forces = resultant force = 0(The acceleration of the object is zero)Unbalanced forces = single force = resultant forceWork = force x distance

Unit is kg m2 s-2 or Joule (J)

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Forces & MotionForces & MotionAll moving objects have kinetic energy (KE) which is due to motion.

KE = mv2Gravitational potential energy is the work done when an object dropped because of downward gravitational pull. PEgravity =

mgh

PEelastic = Fx

Elastic potential energy is work done to stretch or compress a spring or a rubber.

Law of conservation of energyEnergy cannot be made or destroyed, but can change from one form to another.

Efficiency = Useful energy outputEnergy input X 100%

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Forces & MotionForces & MotionPower = rate at which work is done (unit in watt, W)

Power =

Work doneTime taken

Elasticity The property of changing shape when a deforming force acts on an object & returning to the original shape when the force is removed.

Hookes LawThe amount of stretch or compression is directly proportional to the applied force, F.

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SummarySummary

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What you have learned:What you have learned:1.1. Understanding Understanding MotionMotion

2.2. Understanding Understanding MomentumMomentum

Thank YouThank You

3.3. UnderstandingUnderstanding Forces Forces

Chapter 2: Forces & MotionObjectives: (what you will learn) 1) understanding Motion 2) understanding Momentum 3) understanding ForcesSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9