Up Speed Acceleration Motion Graphs 1 Motion Graphs 2 Motion Graphs 3 Resultant Forces Newton's 2nd Law Resistive Forces Stopping Distances Mass and Weight Terminal Speed Hooke's Law Hooke's Law II

 

                                                

 

Rogue Physicist.  Free resources for physics education 2006-2016 Dorian Pascoe.  Email: dorian@top-school.co.uk

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...Forces and Motion...

 

 

 

Lots of forces.

 

 

 

 

The forces and motion module covers work on speed and acceleration, graphical representations of motion using speed-time and distance-time graphs, and looks at ideas about forces and their effects on motion.  It also explores ideas about mass and weight, terminal velocity, and looks at how forces can change the shape of objects.

 

The concepts of elastic and plastic deformation are considered, both in the context of Hooke's law for the extension of springs, and the context of car safety features such as airbags, crumple zones and seatbelts.

 

 

 

 

Lesson

Learning Outcomes

Notes

1 - Speed

  • Explain what is meant by speed

  • Know the units m/s

  • Select and use the equation

speed = dist/time       

Number crunching exercise is the name of the game - stress showing workings and units etc.

2 - Acceleration

  • Explain what is meant by acceleration.

  • Know the units m/s2

  • Select and use the equations:

a = (v-u)/t

and

acceleration = change in speed/time

Developing correct use of vocabulary is essential - pupils should start to use the terms "accelerate and "acceleration" and be clear that accelerating means increasing speed.

It may be helpful to introduce the units as "metres per second each second" to clarify the concept.

3 - Distance/time graphs

 

  • Be able to sketch or plot distance-time graphs for objects moving at constant speed.

  • Be able to interpret distance time graphs to determine whether an object is moving at a constant speed or accelerating.

  • Be able to calculate speed from a distance/time graph, by finding the gradient.

 

4 - Speed/time graphs

  • Be able to sketch or plot speed-time graphs for objects moving at constant speed and constant acceleration.

  • Be able to calculate acceleration and distance travelled from a speed/time graph.

 

 

5 - Resultant Forces

  • Be able to combine multiple forces into a single "resultant force"

  • Be able to describe how a resultant force will change the motion of an object.

 

6 - Force, mass, acceleration

  • Investigate the relationship between force, mass and acceleration.

  • Select and use the equation:

Force = Mass x Acceleration

For Foundation groups concentrate on the qualitative idea that a bigger applied force gives a bigger acceleration (not just 'makes it go faster'!) but a bigger mass is harder to accelerate. Give a few very simple F = ma calculations.

7 - Resistive Forces

  • Carry out a practical to investigate the size of the frictional force acting on a wooden block for a variety of surfaces

Introduce key terms

8 - Stopping distances

  • Carry out a practical task to measure reaction time, and observe the effects of distractions on reaction time.

  • Know the factors that affect thinking distance, and those that affect braking distance.

  • Determine thinking distance, braking distance and total stopping distance by the plotting and analysis of motion graphs or otherwise.

  

Key terms: reaction time, thinking distance, braking distance and stopping distance.

9 - Mass and weight

  • Explain the difference between mass and weight

  • Convert mass/weight using 1kg = 10N on Earth.

Explain difference between mass ( amount of material) and weight (pull of gravity). Show that 1kg = 10N using practical measurement. Practise problems on mass and weight.

Summary - discuss effect of reduced gravity on moon - show video clips.

10 - Terminal Speed

Extended writing opportunity

  • Understand that air resistance acts on moving objects and increases with speed.

  • Explain why falling or moving objects reach terminal speed.

  • Sketch and explain a Speed/Time graph for a falling object.

 

11 - Hooke's law

  • Carry out a practical task to investigate how the extension of a spring varies with the force applied.

  • Know that the extension of a spring is proportional to the force applied, within the elastic region.

  • Be able to use the equation F = k e to solve numerical problems involving the elastic deformation of materials.

 

Key terms: elastic region, plastic region, directly proportional, spring constant, limit of proportionality.

12 - Hooke's law II

  • Understand the terms elastic region, plastic region and limit of proportionality.

  • Be able to sketch and label a graph for a material being stretched.