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Rossana Viola e Maria Bortoluzzi Scientific secondary school Course: technological First class Place: classroom and physics laboratory. MOTION UNDER A CONSTANT FORCE Title: MOTION UNDER A CONSTANT FORCE

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Rossana Viola e Maria Bortoluzzi Skills: to make sense of phenomena students observe and interpret information from a variety of sources. To use appropriate scientific terminology to communicate their conceptual understanding. Present scientific information in written, oral, diagrammatic and graphic forms. Carry out investigative work. Present analyses and evaluations of scientific data in appropriate form.

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Rossana Viola e Maria Bortoluzzi Prerequisites: contents lenght, time, mass, vectors and vector algebra, equations, s-t v-t a-t plots, particle, reference frames and coordinate systems, trajectory and time-law, velocity, acceleration, Straight line motion with a constant speed, covered space as area in a v-t graph.

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Rossana Viola e Maria Bortoluzzi Module planning Teacher activitiesStudents activities interactionCognitive processLanguage demands Language/ learning support Introduces topiclistenWhole classDescribing process Listening vocabulary slides Presents experiment, gives instructions for data processing Listen, copy chartWhole class individual Describing process, apparatus instruction + talk connectors, relevant functions of language Slides black(white-) board, apparatus Monitors, talks to groups and 1:1 Talk in group Fill in diagrams and plots Groupwork pairwork individual Understanding instructions + writing layout Key terms, individual charts, diagrams Elicits reports and conclusions report, draw conclusions Whole classGive and support opinions Blackboard key terms diagrams Presents topicsListenWhole classDescribing process Listen, vocabulary, relevant functions of language + slides Outlines written report respondWhole class groupwork Describing objectives, apparatus,hypothe ses, process,result + report writing frame Gives homework Whole class

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Rossana Viola e Maria Bortoluzzi MOTION UNDER A CONSTANT FORCE MOTION WITH A CONSTANT ACCELERATION

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Rossana Viola e Maria Bortoluzzi VOCABULARY: Velocity :Velocity : vettore velocità. Speed :Speed : modulo del vettore velocità. Grade :Grade : pendenza di una retta in un sistema di riferimento (piano cartesiano) Air-bearing rail:Air-bearing rail: rotaia a cuscinetto daria.

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Rossana Viola e Maria Bortoluzzi

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But they are difficult motions to describe because of their irregular speed variations !

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Rossana Viola e Maria Bortoluzzi There is a natural motion in which speed variation in time is almost regular: its the motion of drop of a body close to the earths surface It may be described in a simple enough way!

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Rossana Viola e Maria Bortoluzzi In figure a sphere drop is represented. It has been photographed at equal intervals t= 0.05 s. In following intervals t the distance covered by the sphere is not constant but it progressively increases.

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Rossana Viola e Maria Bortoluzzi Activity: AIM: represent in a speed - time plot the values of average speeds of the sphere in considered intervals t calculated through the relation : Δt (s)t (s)Δs (cm)v (cm/s) 0.00000 0.05 1.530 0.050.13.5 0.050.15 0.05

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Rossana Viola e Maria Bortoluzzi t (s) Δs (cm) v (cm/s) 0.0000 0.051.530 0.13.570 0.156.0120 0.28.5170 0.2511.0220 0.313.5270 0.3516.2324 0.418.3366 0.4521.0420 Speed and time are directly proportional quantities !!

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Rossana Viola e Maria Bortoluzzi We know that Thus we obtain the speed-time relation: with a = constant. If and that relation becomes or, in general, v=aּt with a = constant.

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Rossana Viola e Maria Bortoluzzi v = aּt is the equation of the line in previous graph. a is the grade of that line: the greater the acceleration is, the greater the grade will be. For example:

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Rossana Viola e Maria Bortoluzzi acceleration-time plot The graph is a time axis parallel segment. At time variation, acceleration takes the same value.

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Rossana Viola e Maria Bortoluzzi We know that in a speed-time plot the area A under the line represents the distance covered by the point in motion in considered time interval. Lets deduce the space-time relation: area A is but v=at, thus therefore time law A

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Rossana Viola e Maria Bortoluzzi Activity Represent the space-time plot t (s)s (cm) 0.000 0.051.5 0.15 0.15 0.2 0.25 0.3 0.35 0.4 0.45

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Rossana Viola e Maria Bortoluzzi Activity Represent the space-time plot Its a parabolic curve. Theres a quadratic relation between space and time t (s)s (cm) 0.000 0.051.5 0.14 0.1511 0.219.5 0.2530.5 0.344 0.3560.2 0.478.5 0.4599.5

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Rossana Viola e Maria Bortoluzzi exercise some Complete following text with some of the words at the bottom of this slide. According to ………s second law, F=ma, if the …… acting on a particle remains constant in magnitude and direction, the point will move in a ………… with a constant acceleration. This means that the point will acquire equal increments of velocity in equal ……………. Galileo force Newton space time intervals parabolic curve Giuseppe straight line

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Rossana Viola e Maria Bortoluzzi exercise some Complete following text with some of the words at the bottom of this slide. According to ………s second law, F=ma, if the …… acting on a particle remains constant in magnitude and direction, the point will move in a ………… with a constant acceleration. This means that the point will acquire equal increments of velocity in equal ……………. Galileo force Newton space time intervals parabolic curve Giuseppe straight line Newtonforce straight line time intervals

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Rossana Viola e Maria Bortoluzzi exercise A car moves and in 5 seconds covers a distance s=100m. Assuming that the car has a constant acceleration, calculate the value of acceleration and than the speed at the end of these 5 seconds.

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Rossana Viola e Maria Bortoluzzi exercise A car moves and in 5 seconds covers a distance s=100m. Assuming that the car has a constant acceleration, calculate the value of acceleration and than the speed at the end of these 5 seconds.

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Rossana Viola e Maria Bortoluzzi Laboratory experiment Aim: to study a straight line motion with a costant acceleration. Equipment: air-bearing rail. Gathered data: space (s) and time (t). Data processing: calculation of speed (v), acceleration (a) and mean value of acceleration. Make a table with all these values. Required plots: 1) space-time 2) speed-time 3) acceleration-time.

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Rossana Viola e Maria Bortoluzzi What to do: 1) make a REPORT. 2) fill in a GOWIN CONCEPT MAP like this: Theoretical-conceptual side Methodological side Focal request: Concepts: Theory: Equipment: Evaluation statements: Knowledge statements: Data processing: Gathered data: Event:

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Rossana Viola e Maria Bortoluzzi What to do: 1) make a REPORT. 2) fill in a GOWIN CONCEPT MAP like this: Theoretical-conceptual side Methodological side Focal request: How to study a straight line motion with a constant acceleration? Concepts: s, t, v, a Theory: v=at s=1/2 at^2 Error theory Equipment: Air-bearing rail Evaluation statements: At the start its better push the truck with an electromagnetic device than manually. Knowledge statements: a(m)=…… Data processing: Calculation of v, a, a(m). s-t v-t a-t plots Gathered data: s,t Event: The truck slides on the rail.

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