Year 5 Science Forces – Block 5F – May The Forces Be With You

Session 5:The Goldilocks Path Challenge
Science curriculumarea: Forces / ii. identify the effects of friction, that acts between moving surfaces
Working Scientifically (UKS2 WS) /
  1. planning different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary
  2. taking measurements, using a range of scientific equipment, with increasing accuracy and precision, taking repeat readings when appropriate
  3. recording data and results of increasing complexity using scientific diagrams and labels, tables, scatter graphs, bar and line graphs
  4. using test results to make predictions to set up further comparative and fair tests
  5. reporting and presenting findings from enquiries, including conclusions, causal relationships and explanations of and degree of trust in results, in oral and written forms such as displays and other presentations

Teaching Objectives /
  • Investigate the effect ground friction has on movement
  • Identify an appropriate amount of friction for the safe onward journey of a bike
  • Use results to make further predictions and suggest further investigation

Key Vocabulary:variables, accuracy, precision, gravity, friction, moving surfaces, mechanisms, gears, transfers
Resources
Three path images, force meter, access to mud, tarmac and a tiled floor, relatively ‘heavy’ cars/vehicles for testing / Weblinks
- Forces, Friction and Gravity – 10:40 –end;- Wind resistance in cycling; - Friction.
Whole Class:Have a muddy area, playground and tiled floor ready for the testing phase. Explain that you have had an urgent text message through saying that the team has come to a standstill at ajunction that has three paths stretching down into the valley. Each path has a different ground surface (smooth rock, tarmac, mud (wet)). The team wants to know which is the best for their bikes, so that they don’t go too fast (their brakes have broken!), but that they also don’t get stuck. Show chn the three paths and ask them for an initial assessment - what is it that makes them think one will be slippy, while another might be slow? Talk about friction and watch the first video. Chn may have carried out investigations into friction in the past with cars and ramps- explain that for this investigation the team specifically wants to know about the amount of forces involved so you would like them to use a force metre and the three ground coverings to see how much of a force is needed to get the bike across each terrain. From these results you want chn to make predictions about how the friction created on each path might impact on the speed and effort required to cycle on it. Knowing this, ask chn to come up with a specific enquiry question (What impact does friction have on the force needed for a bike to travel forwards?).
Activities:Get chn to work in mixed ability gps, using questioning to stretch and support.The dilemma of the three paths - ask chn to work out which path is the ‘Goldilocks path’ - not too fast and not too slow, but just right. Test out a relatively heavy car and measure the friction resistance force using a force meter. Chn will need to come up with a suggested approach to their investigation, identifying the thing that they will change each time and what they will keep constant. Note the accuracy with which chn carry out their investigation and get them to record their results in a format of their choice. Challenge chn to suggest the effort each terrain would require if cycling and see if they can suggest a gear combination from Session 4 that might be the best choice for each surface. What are their findings and how do they think this would relate to speed for each surface? Encourage chn to talk about whether each level of friction would slow, maintain speed or accelerate a bike if the input from the cyclist remained constant. Remind chn of Newton’s 1st Law of Motion - that an object either stays at rest or continues to move at a constant speed, unless another force acts upon it. What is the friction doing in terms of Newton’s law of motion? Can chn suggest how we could investigate this (cars down a ramp investigation!). Get chn to create a graph to send to the recovery team to share their findings - get chn to choose the graph type (see examples) and to include a statement for each path about predicted speed.
Plenary / Share findings and see if everyone agrees. Ask chn why they think the path that seems to have the least amount of friction is not necessarily the path that the bikes want to use (they might crash!). How do chn think brakes work? When do you use brakes on a bike? How do chn think they affect the grip of the bike on the ground? (Increases the fiction between the brake ‘pad’ and the wheel, causing the bike to slow down as the wheels won’t turn.) What other form of friction might affect the journey? Air resistance -noted in Session 4 (watch bike video).Homework: chn explore the test track here:
Outcomes / Children will
  • Investigate the effect of ground friction on the force needed to move a toy car
  • Recommend a ground covering that creates the right level of friction for the safe onward journey of a bike
  • Predict the likely speed of a bike on different surfaces, based on findings from friction investigation

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