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

Session 3:The Lever and Pulley Challenge
Science curriculum area: Forces /
  1. explain that unsupported objects fall towards the Earth because of the force of gravity acting between the Earth and the falling object
iii. recognise that some mechanisms, including levers and pulleys, allow a smaller force to have a greater
effect
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 and tables
  4. using test results to make predictions to set up further comparative and fair tests
  5. report and presenting findings from enquiries, including conclusions, causal relationships and explanations of and degree of trust in results, in written forms

Teaching Objectives /
  • Investigate how levers work; exploring how the position of fulcrum, load and effort impacts on use
  • Investigate how pulleys work and how the number of pulleys used changes the effort required
  • Draw diagrams that explain the forces, loads, weights and efforts for levers and pulleys

Other Curriculumareas / Maths
  • Use all four operations to solve problems involving measure using decimal notation, including scaling
  • Scale weights and lengths using appropriate calculations

Key Vocabulary:variables, accuracy, precision, causal relationships, gravity, mechanisms, levers, pulleys, transfers
Resources
Transcript from NHM recovery team phone call, types of lever, lever investigation guidance (child facing) & equipment, pulley images, instructions and guidance, calculations for positioning a fulcrum. / Weblinks
Whole Class:Make some tabletop seesaws using balsa wood. Explain that you have had contact from the recovery team to say that the meteorite is in a big hole (crater). The reception was poor due to their remote location and you only got some of the message. Read the transcript and ask chn how they think a wooden plank, a rock, rope, old oil cans and a ground sheet are going to help.Do they know whatlevers and pulley systems are? Note that levers can help lift a very heavy object using a much smaller force.Get chn to try and ‘balance’ a seesaw, (a type of lever), using weighted Lego™ figures. Howdid they do it? Now get them to move one Lego™ person closer to the middle of the seesaw – what happens? (That Lego™ person goes up – the seesaw is unbalanced, as are the forces.) Try again, but this time move the balancing platform (explain that we call this a fulcrum). Can the chn make some generalised statements about what they have just seen (moving one weight closer to the fulcrum has what effect? Moving the fulcrum has what effect?) What is it that causes the seesaw to go down? (Gravity acting on the Lego™ figure) - it needs an opposite/resistance force (weight of other figure) to balance it or move it upwards. Ask chn how using a lever would help the recovery team.Get chn to suggest a specific enquiry question, e.g. does moving the position of the fulcrum increase or decrease the input force? Once out of the crater, how can the meteorite be moved onto a vehicle?Look at the other equipment the team told you they have (rope, old oil cans, ground sheet). Show chn the pulley images and explain that a pulley can change the direction a force acts in, making a small input force sufficient to lift a heavy object.Explain that chn need to offer advice on how to position the fulcrum, load and effort to get the meteorite up so as to be able to get the ground sheet underneath and hooked up to the pulley system. What could they do to work this out through investigation (see questions)?
Activities:chn to work in mixed ability gps spending 20 mins on eachLever investigation (chn to complete independently): remind chn that the meteorite weighs 200kgwhile the two heaviest members of the team each weigh 70kg - get chn to work out an equivalent ratio and prep their investigation including variables (see guidance).Explain that on Earth you will roughly have 10 newtons (N) for every one kg.Pulley investigation:come up with the pulley enquiry question and support chn as they make and test out two pulley systems (see guidance). Encourage chn to experiment with the number of cotton reels used.Lever/pulley hunt- give chn images of lever types and get them find as many examples of each as they can in the classroom and online. Do the same for pulleys.
Plenary / Get chn to share their ideas and note that there are two options for the fulcrum – moving the position of the weight in relation to the fulcrum, OR increasing the force applied (i.e. more of the team pushing, although this could get rather crowded!) - note that often in science there may be more than one plausible solution to a problem.Ask chn about their pulley findings. Look at the mathematical formula for positioning a fulcrum and see if chn can help calculatehow they as individuals could lift a range of heavy objects (e.g. a 65kgadult).
Outcomes / Children will
  • Investigate how levers work and how the position of the fulcrum impacts on its effectiveness
  • Scale weights and lengths
  • Investigate how pulleys work and note the correlation between effort required and the number of pulleys
  • Set out instructions for forces on the ground to help them implement findings from investigations

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