# P2.2.1 Forces and Energy P2 Physics Ks4 Additional Science Mr D Powell.

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P2.2.1 Forces and Energy P2 Physics Ks4 Additional Science Mr D Powell

Connection Connect your learning to the content of the lesson Share the process by which the learning will actually take place Explore the outcomes of the learning, emphasising why this will be beneficial for the learner Demonstration Use formative feedback – Assessment for Learning Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex Offer different ways for the students to demonstrate their understanding Allow the students to “show off” their learning Consolidation Structure active reflection on the lesson content and the process of learning Seek transfer between “subjects” Review the learning from this lesson and preview the learning for the next Promote ways in which the students will remember A “news broadcast” approach to learning Activation Construct problem-solving challenges for the students Use a multi-sensory approach – VAK Promote a language of learning to enable the students to talk about their progress or obstacles to it Learning as an active process, so the students aren’t passive receptors

P2.2.1 Forces and Energy W = F x d P = E/t
When a force causes an object to move through a distance work is done. Work done, force and distance, are related by the equation: W = F x d Energy is transferred when work is done. (Candidates should be able to discuss the transfer of KE i.e... shuttle re-entry or meteorites burning up in the) Work done against frictional forces. Power is the work done or energy transferred in a given time. P = E/t W = F x d P = E/t

Formulae help... W = F x d P = E/t Ep = mgh Ek = ½ mv2

When I move these objects I do what...

A C/D 2J 15J 1200J a/b) What is work done?
TASK: Summarise this idea then answer the questions C/D When I move an apple (1N weight) a distance of 2m along a desk what is the work done? When I move 0.5kg a distance of 3m along a desk what is the work done? When a weight lifter lifts a weight of 80kg a height of 1.5m what is the work done? (mgh) 2J 15J 1200J

D B/C a/b) More on W.D. TASK: Explaining / Devising
Using the formulae for reference can you explain what happens to the W.D. If you have a bigger mass or larger distance to move your object? Can you think of a formulae which could relate Power to Work Done. Write it out and explain how it works.... Write out your own example of a “worked problem” for another situation

D Friction at work TASK: Explain several examples where friction effects your life. C

D Plenary... 96J 90 & 4500J WD= mgh or WD/mg= h = 270J/450N = 0.6m

Power P = E/t This is a very easy thing to look at when we consider work done. Before we have looked at how energy is transferred via work done (see example below). If you want to think about the power you simply divide the energy transferred by how long it to transfer...

D Multichoice

D Summary Questions II WD = Fd = 20N x 1.5m = 30Nm = 30J
WD = Fd = 600N x 100m = 60,000Nm = 60,000J = 60kJ WD = Fd = 3000N x 30m = 90,000Nm = 90,000J = 90kJ E = Pt so E / t = P = 60,000J / 20s = 3000J/s = 3000W E = Pt so E / t = P = 90,000J / 20s = 4500J/s = 4500W

P2.2.1 Forces and Energy Ep = mgh Ek = ½ mv2
e) Gravitational potential energy is the energy that an object has by virtue of its position in a gravitational field. Ep = mgh f) The kinetic energy of an object depends on its mass and its speed. Ek = ½ mv2 Ep = mgh Ek = ½ mv2

S What happens here.... Where has the energy gone?
What is happening... What happens here.... Where has the energy gone?

Pendulum... Label the diagram with the energy changes...

Where does it come from?

Interactive

Kinetic Energy of a horse..
A horse (with 3 legs) of mass 175kg walks at a velocity of 3ms-1 its kinetic energy is found as; Quick Version.....

Another worked example?

Sorting.... TASK: Firstly work in a pair and guess sort these vehicles then work out the missing KE values and then sort them into which has the largest and which has the smallest? A/B 2250 kgm2s-2 or 2250J 1000 kgm2s-2 or 1000J 187.5 kgm2s-2 or 187.5J 100 kgm2s-2 or 100J 2000 kgm2s-2 or 2000J NB: take care with your units for KE

Practical Examination of Kinetic Energy
D Practical Examination of Kinetic Energy The kinetic energy of an object is the energy it has due to its motion. It depends on its mass and its speed We can investigate how the kinetic energy of a ball depends on its speed. The ball is released on a slope from a measured height above the foot of the slope. We can calculate the gravitational potential energy it loses from its weight and its drop of height. The kinetic energy it gains is equal to its loss of gravitational potential energy. The ball is timed, using light gates, over a measured distance between X and Y after the slope. Q) How do light gates improve the quality of the data you can collect in this investigation?

Practical Examination of Kinetic Energy (HT)
D Practical Examination of Kinetic Energy (HT) Here are some results for a 0.5kg ball which has been dropped. Can you work out the missing values if the formulas are; EGPE = mgh EKE = ½mv2 d/t = v ∆h (m) 0.05 0.1 0.16 0.20 PE of ball (J) 0.25 0.72 1.00 ∆t to travel 1m from x -> y 0.98 0.57 0.50 Velocity ms-1 1.02 2.00 0.80 0.71 1.41 1.75 TASK: Complete the table by doing 4 calculations. There two ways of thinking about it! A/B

Multichoice PE = mgh KE = ½mv w = mg

H W A U orking nswer nit Homework Questions...
TASK: You have these 6 questions on a worksheet to fill in and then check next lesson. Work out the kinetic energy of a fighter aircraft with a mass of 195kg travelling at a speed of 666ms-1. What is the significance of the speed of the fighter aircraft? The designers of the Euro fighter Jet want to improve the acceleration of the plane. How can they achieve this without using larger engines? Justify you answer? If the mass of the plane doubles by what factor does the kinetic energy increase for the same speed? If the velocity of the plane increases by a factor of x3 by what factor does the kinetic energy increase. A passenger plane burns up 70kg of fuel which contains 1050J of energy to get to a height of 700m. Taking account that the plane is 70% efficient, how much potential energy does the plane now have at this height? W orking A nswer U nit

H W A U orking nswer nit Answers.... See right.......
2) twice the speed of sound; mach 2 3) F=ma, reduce the mass. Since the acceleration will be increased therefore the force is reduced to accelerate the plane. Same argument also applies to streamlining 4) x2 5) x9 or 32 6) 1050J x 0.7 or (1050J x 70%) /100% gives; 735J. The 30% of wasted energy is lost in heat to the surroundings. W orking A nswer U nit

Ep = mgh A-B W.D. In context TASK:
Logically reason out what is happening in the diagram. Draw out your own copy and label what is going on. Compare what is happening here to the formulae you have already covered. (Hint: W = mg) Ep = mgh A-B

You have 2 minutes to rearrange and sort out these formulae
Formulae Warm Up...... You have 2 minutes to rearrange and sort out these formulae Simplify? 2 1) Make the square the subject? 2) 2 Find the triangle? 3)

You have 2 minutes to rearrange and sort out this formulae
to get make the following the subject... v = m = be prepared to come up to the board and demonstrate how you got there!

EGPE = mgh (eq1) EKE = 0.5mv2 (eq2) Back to waterfalls...
We can also do something clever when thinking of this formula when looking at Kinetic Energy as well. EGPE = mgh (eq1) EKE = 0.5mv (eq2) If I think of a transfer involving the energy at the top of a waterfall (GPE) and energy at the bottom (mainly KE) I can work out the speed of the water falling by equating the two equations and assuming all the energy is transferred to kinetic. In every case we find a value of “g” gravity as 10 m/s2

What is the speed of the water...
Using this idea can you apply the formula and fill in the grid for water which drops from different heights. You will need to use the Sqrt button on your calculator... h (m) V (in m/s) 5 10.00 10 14.14 20 20.00 100 44.7 h (m) V (in m/s) 5 10 20 100

Physics of Space Battles - Advanced
Task: Now you have watch the movie make a comment in your own words (you can use my help) to explain what you have seen. What do you think? (1 paragraph) We think of the EM spectrum from Year 10 as having more energy as  (wavelength) is shorter. (think UV -> Gamma) The actual reason for this is because the energy for each photon of light is found from E=hf. (h is a constant, f = frequency ) But what about simply using a matter thrower. Energy of particles is found from 0.5mv2 Just throw rocks fast enough and they have lots of energy!

Plenary Questions Task: Do these questions / activities on your own without help from anyone! Copy down the equation for Kinetic Energy in your book. Use the formulae to explain why an object with more mass would have more KE. (explain in detail) Use the formulae to explain why an object with double the velocity would have four times the KE. (explain in detail What is the main point of the movie you saw in relation to “space physics” Calculate the kinetic energy of a ball of mass 0.5kg thrown at a speed of 5ms-1

Extension Quick Questions
PE = mgh KE = ½mv w = mg KE = ½mv2 = 0.5 x 80 x 102 = 4000J KE = ½mv2 = 0.5 x 500 x 302 = 225kJ KE = ½mv2 = 0.5 x 10,000 x 2002 = 9MJ PE = mgh = 10m x 10 N/kg x 100kg = 10,000 Nm = 10,000J = 10KJ PE = mgh = 3000m x 10 N/kg x 60kg = 1,800,000 Nm = 1.8MJ PE = mgh = 50m x 10 N/kg x 0.100kg = 50 Nm = 50J

Multichoice...

P2.2.1 Forces and Energy When a force causes an object to move through a distance work is done. Work done, force and distance, are related by the equation: W = F x d Energy is transferred when work is done. (Candidates should be able to discuss the transfer of KE i.e... shuttle re-entry or meteorites burning up in the) Work done against frictional forces. Power is the work done or energy transferred in a given time. P = E/t Gravitational potential energy is the energy that an object has by virtue of its position in a gravitational field. Ep = mgh The kinetic energy of an object depends on its mass and its speed. Ek = ½ mv2 P2.2.1 Forces and Energy When a force causes an object to move through a distance work is done. Work done, force and distance, are related by the equation: W = F x d Energy is transferred when work is done. (Candidates should be able to discuss the transfer of KE i.e... shuttle re-entry or meteorites burning up in the) Work done against frictional forces. Power is the work done or energy transferred in a given time. P = E/t Gravitational potential energy is the energy that an object has by virtue of its position in a gravitational field. Ep = mgh The kinetic energy of an object depends on its mass and its speed. Ek = ½ mv2 P2.2.1 Forces and Energy When a force causes an object to move through a distance work is done. Work done, force and distance, are related by the equation: W = F x d Energy is transferred when work is done. (Candidates should be able to discuss the transfer of KE i.e... shuttle re-entry or meteorites burning up in the) Work done against frictional forces. Power is the work done or energy transferred in a given time. P = E/t Gravitational potential energy is the energy that an object has by virtue of its position in a gravitational field. Ep = mgh The kinetic energy of an object depends on its mass and its speed. Ek = ½ mv2

Formulae help... W = F x d P = E/t Ep = mgh Ek = ½ mv2

Formulae help... W = F x d P = E/t Ep = mgh Ek = ½ mv2

Work Done Revision Work Done Revision

KE & PE Revision KE & PE Revision

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