Presentation on theme: "P2.2.2 Momentum P2 Physics Ks4 Additional Science Mr D Powell."— Presentation transcript:
1 P2.2.2 MomentumP2 PhysicsKs4 Additional ScienceMr D Powell
2 ConnectionConnect your learning to the content of the lessonShare the process by which the learning will actually take placeExplore the outcomes of the learning, emphasising why this will be beneficial for the learnerDemonstrationUse formative feedback – Assessment for LearningVary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sexOffer different ways for the students to demonstrate their understandingAllow the students to “show off” their learningConsolidationStructure active reflection on the lesson content and the process of learningSeek transfer between “subjects”Review the learning from this lesson and preview the learning for the nextPromote ways in which the students will rememberA “news broadcast” approach to learningActivationConstruct problem-solving challenges for the studentsUse a multi-sensory approach – VAKPromote a language of learning to enable the students to talk about their progress or obstacles to itLearning as an active process, so the students aren’t passive receptors
4 P2.2.2 Momentum Momentum is a property of moving objects. p = m x v In a closed system the total momentum before an event is equal to the total momentum after the event. This is called conservation of momentum.p is momentum in kilograms metres per second, kg m/sm is the mass in kilograms, kgv is the velocity in metres per second, m/sCandidates may be required to complete calculations involving two objects. Examples of events are collisions and explosions.
5 Practical / DemoSuggested ideas for practical/demonstrations to develop skills and understanding include the following:investigating the transfer of Ep to Ek by dropping a card through a light gate.plan and carry out an investigation to measure velocity using trolleys and ramps.running upstairs and calculating work done and power, lifting weights to measure power.a motor lifting a load to show how power changes with load.stretching different materials before using as catapults to show the different amounts of energy transferred, indicated by speed reached by the object or distance travelled.
6 AMomentum DefinedMomentum is important to anyone who plays a contact sport. In a game of rugby, a player with a lot of momentum is very difficult to stop.The momentum of a moving object = its mass x velocity.momentum = mvThe unit of momentum is the kilogram meter/second (kg m/s).Calculate the momentum of a 40 kg person running at 6 m/s.Calculate the momentum of a 80 kg person running at 3 m/s.Calculate the velocity of a 80 kg bike with momentum of 2kg m/s.Calculate the mass of a person with momentum of 2kg m/s and velocity of 0.02 m/s240kg m/s0.025m/s100kg
7 Investigating Momentum Simply... Using only your fingers, a few similar coins, the desk, a stopclock and ruler can you explore the concept of momentum and come up with any rules of thumb or prove the formulae.The momentum of a moving object = its mass x velocityp = mvYou could investigate?Distance of travelMass movedFlick strengthTime of travelAverage Speed /VelocityPick a variable to keep the samePick a variable to changeMake a tableRecord your resultsMake a comment
8 p = mu or p = mass x flick speed ResultsThese results broadly show that if we double the mass of the object the distance travelled by the object for the same flick halves.Hence if we doubled the flick force each time we doubled the mass it would make sense that the coin would then move as far each time!Why not think in terms of flick as the intital velocity uHence:p = mu or p = mass x flick speedMomentum changes as mass changes…..Number of CoinsDistance Travelled in m10.4520.2430.1640.1450.09
9 AMars LandersAnother interesting idea about momentum is looking at the change in momentum during a collision.When you stop suddenly (i.e. land on mars) your velocity changes quickly and there is an initial and final velocity. Also a force on you and a time that it happens it. The formulae for this is;You are going to explore this idea by making a Mars lander for a fresh egg. The idea is to make the force on the egg as little as possible over the crash as you drop it from as high as possible. If you kill egg your pilot is dead!You have 25 minutes to design your craft & your equipment is;1 x egg8 x A4 paper1 x 3m strip of sticky tape3 x human brains per team v=final velu = initial velt = timeF = force
10 D momentum = mass x velocity Comparing Momentummomentum = mass x velocityWe can also easily see that an object with;more massmore velocitymore mass and velocityWill have a larger momentum;30m/s6000kg3180,000 kg m/s125m/s1000kg10m/s6000kg425,000 kg m/s250m/s1000kg60,000 kg m/s50,000 kg m/s
11 Investigating Collisions When two objects collide, the momentum of each object changes.;Trolley A is given a push so it collides with a stationary trolley B.The two trolleys stick together after the collision. (bluetac)The computer gives the velocity of A before the collision and the velocity of both trolleys afterwards.Before and after the collisionThe mass of trolley B absorbs some of the KE of trolley AmAvA + mBvB = mABvABWhat does each section of the velocity–time graph show?Why does the velocity reduce?Can you come up with any written formulae from what you know about momentum to describe the change?
12 Investigating Collisions In fact we can use the generic formulae;mAvA + mBvB = mABvABTo describe any change in momentum for this type of collision. Also you may see the trucks called Number 1 & 2For two trolleys of the same mass, the velocity of trolley A is halved by the impact. The combined mass after the collision is twice the moving mass before the collision. So the momentum (mass x velocity) after the collision is the same as before the collision.For a single trolley pushed into a double trolley, the velocity of A is reduced to one-third. The combined mass after the collision is three times the initial mass. So once again, momentum after the collision is the same as the momentum before the collision.
13 Worked Example..TASK: Read this information here ( stick the print out in your book) Can you do your own worked example which is similar....A
14 A mAvA + mBvB = mABvAB Car shunts... If a vehicle crashes into the back of a line of cars, each car in turn is ‘shunted’into the one in front. Momentum is transferred along the line of cars to the oneat the front.If you have ever been in one of these or seen one of these where does the energy eventually go?What do you think that we must assume when completing simple calculations on momentum in the exam?mAvA + mBvB = mABvAB
17 AMomentumIf we are considering mass and velocity we can combine them into a more useful form which describes both at the same time and allows comparisons between events and objects.We can say thatmomentum = mass x velocityIt is also important to realise that velocity is a directional quantity so it can be negative or positive.30m/s- 30m/s
18 Bounces Crashes / Collision When these trucks bounce off each other we consider that all the momentum is transferred to the blue truckWhen these trucks connect to each other we consider that the momentum is shared between blue truck & red truck
19 A mAvA + mBvB = 0 Or rearange; mAvA = -mBvB Explosions...In explosion trolley examples:momentum of A after = mAvAmomentum of B after = mBvBtotal momentum before = 0 (because both trolleys were at rest).Using conservation of momentum gives:mAvA + mBvB = 0Or rearange;mAvA = -mBvBThis tells us that A and B move apart with equal and opposite amounts ofMomentum and the idea of velocity being a vector is shown!TASK: Read this information then write a note entitled “What is an explosion” (in terms of momentum)
20 D mAvA = -mBvB Explosions in guns... When a shell is fired from an artillery gun, the gun barrel recoils backwards.The recoil of the gun barrel is slowed down by a spring. This lessens the backwards motion of the gun. An artillery gun of mass 2000 kg fires a shell of mass 20 kg at a velocity of 120m/s. Calculate the recoil velocity of the gun?mAvA = -mBvBTASK: Write down this example (in brief) for your book & calculate the velocity.....
21 CPlenary Question...A 600kg cannon recoils at a speed of 0.5m/s when a 12kg cannon ball is fired from it.Write out the formulae you will use.Rearrange to calculate the velocity of the cannon ball when it leaves the cannon.Make sure you include a unit in your answermAvA = -mBvB
25 AForce & MomentumF=ma&(v-u)/t = aSub in for “a”
26 A What does it mean? The equation shows that: Making the time longer (increasing the value of t) makes the force smaller. Crumple zones in cars are designed to make impact times longer so impact forces are reduced.When a resultant force acts on a moving object, a change of momentumtakes place. In general, the force needed to cause a change of momentum is given by:
27 DExample.....Scientists at Oxford University have developed new lightweight material for bullet-proof vests.The material is so strong and elastic that bullets bounce off it. A bullet of mass kg moving at a velocity of 90 m/s is stopped by a bulletproof vest in s. What is the impact force?Now try the same calculation but with a time of sNow try the same calculation but with a mass of 0.008kg?Now try same calculation but with a velocity of 120m/st = 2/3 so F = -1800Nm = x2 so F = -2400Nv = 4/3 so F = -1600N
33 TASKYou have now watched the horizon movie on crash testing can you write an extended paragraph including your own comments and thoughts on;What were they trying to do?What is the Physics of the situation ?What tests were completed; cadavers, live, animals, dummies.Why did they test them?Do you agree or disagree with what was doneWhat part do the car companies play in the grand scheme of thingsWhat changes have occurred in society in the past 80 years?
35 P2.2.2 MomentumMomentum is a property of moving objects.p = m x vIn a closed system the total momentum before an event is equal to the total momentum after the event. This is called “conservation of momentum”.p is momentum in kilograms metres per second, kg m/sm is the mass in kilograms, kgv is the velocity in metres per second, m/sCandidates may be required to complete calculations involving two objects.Examples of events are collisions and explosions.P2.2.2 MomentumMomentum is a property of moving objects.p = m x vIn a closed system the total momentum before an event is equal to the total momentum after the event. This is called “conservation of momentum”.p is momentum in kilograms metres per second, kg m/sm is the mass in kilograms, kgv is the velocity in metres per second, m/sCandidates may be required to complete calculations involving two objects.Examples of events are collisions and explosions.P2.2.2 MomentumMomentum is a property of moving objects.p = m x vIn a closed system the total momentum before an event is equal to the total momentum after the event. This is called “conservation of momentum”.p is momentum in kilograms metres per second, kg m/sm is the mass in kilograms, kgv is the velocity in metres per second, m/sCandidates may be required to complete calculations involving two objects.Examples of events are collisions and explosions.