Using physics to measure the power of your bicep


This experiment uses two important pieces of Physics:



Work Done (Joules J) = Force (Newtons N) x Distance moved in direction of force (m)
Work done is the energy required to apply a force to move something a distance. As with all energy, it is measured in Joules (J)

Power (Watts W) = Work done/time taken (s)
Power (measured in Watts) is how quickly work is done. It is sometimes called the rate of energy transfer.

You need to learn and remember both of these equations

The Experiment

Part 1 – Measuring how much energy it takes to lift a mass (calculating the Work done)


You will be lifting a 1kg mass (or more/less if you wish) from the lowest point your arm can reach (when it is straight by your side) to the point where the mass is touching your shoulder.
If you lift the mass this distance then you are pushing the mass upwards with a force equal to its weight and moving it a distance equal in length to your arm.

Measure the length of your arm from the centre of your palm to your shoulder and write this length IN METRES.


The weight of the mass is the force with which the earth is pulling the mass down to the ground with and this is the same as the force you are pushing up on the mass with in order to lift it.
We calculate this force by multiplying the mass in kg by the gravitational field strength. On earth the gravitational field strength is 10 N/kg.



The energy you’ve used to lift the mass is the work done:
 

Work done = Force x Distance moved in direction of force =                                                                   J
(should be between 5J and 15J)

Part 2 – Calculating the Power of your bicep in Watts
Working in pairs, you need to count how many times you can lift the mass in 30 seconds. Do this as fast as you can making sure you are lifting the mass through the full height each lift. Have your partner measure the time, count and check you are doing the exercise correctly.
 

Number of lifts in 30 seconds =

Total Energy used = Work done for one lift (what you calculated above) x number of lifts
 

Power = Work done/time = Total energy used/30 =                                                          W


Edexcel GCSE Chemistry Core Practical 1 - Investigating the composition of inks


This practical is in two sections – simple distillation and paper chromatography of inks. You can carry out the practical in one session or two, depending on the length of your lesson. Many of your students will have carried out these practicals as part of their Key Stage 3 course so this activity can be used to revise the techniques as well as introduce the additional theory required for chromatography.


FOR THE CHROMATOGRAPHY PART OF THE PRACTICAL:

Questions you could ask to enhance learning and focus your students on important aspects of the practical: 


  • Why is it important to draw the lines and write labels on the chromatography paper in pencil and not in ink?
  • Why should the spots of ink be above the level of the solvent in the beaker?
  • What is meant by the term ‘solvent front’?
  • What would happen if you used permanent ink instead of water soluble ink? How could you overcome this problem?
  • Which is the mobile phase? Which is the stationary phase?
  • Which ink(s), if any, contain one dye? Which ink(s) are mixtures of dyes? Which inks contain the same dye? 
Skills that are covered in the practical:

  • Measuring distance travelled by solvent
  • Measuring height of dye above start line (estimate to centre of spot)
  • Ability to manipulate apparatus for chromatography, recording observations (e.g. number of dyes in each ink, distance travelled by solvent, height of each dye above start line)
  • Ability to carry out investigation safely 
Maths Skills:

  • Interpreting a chromatogram
  • Recording measurements accurately (1 dp)
  • Substituting values correctly into expression for Rf, calculating the Rf value for the different dyes, giving answer to an appropriate number of significant figures 

FOR THE DISTILLATION PART OF THE PRACTICAL:

Questions you could ask to enhance learning and focus your students on important aspects of the practical: 

  • Why do you need to heat the tube of ink gently?
  • What is the temperature on the thermometer when the water is distilling off?
  • Why does the collection tube need to be surrounded by crushed ice?
  • What are the main errors in this procedure?
  • How can you improve the procedure? 
Skills that are covered in the practical:

  • Measuring the temperature
  • Ability to heat gently and safely
  • Ability to manipulate apparatus for simple distillation
  • Recording observations (e.g. colour of distillate)
  • Ability to carry out investigation safely 
Maths Skills:
  • Not relevant to this part of the experiment

Edexcel GCSE Physics Core Practical 2 - Measuring Waves in Solids and Liquids


The emphasis in this practical should be on the different methods needed to measure these quantities for the different waves. For water waves, the speed, frequency and wavelength can all be measured separately, but the speed of sound in a solid is too fast to be measured by simply measuring distance and time. Here, the speed is calculated using the measurements made of frequency and wavelength.

Questions you could ask to enhance learning and focus your students on important aspects of the practical:

  • Waves can be transverse or longitudinal. What type of wave is (a) a water wave on the surface of the water in a ripple tank? (b) a sound wave in a metal rod?
  • How would you measure the speed of sound in air?
  • How would you measure the speed of water waves in a ripple tank?
  • Why can you not measure the speed of sound waves in a metal rod in the same way?
  • Is it possible to measure the speed of light? 
Skills that are covered in the practical: 

  • Adjusting the components of a ripple tank to give parallel water waves of measurable wavelength
  • Measuring the wavelength of a water wave in a ripple tank
  • Measuring the speed of a wavefront (wave crest) 
Maths skills: 

  • Substituting measured values into the equation relating speed, distance and time 
  • Substituting measured values into the equation relating speed, wavelength and frequency
  • Changing the subject of an equation 



P3 Physics revision questions Edexcel AQA GCSE

QUESTIONS
1.       What type of image do x-rays form?
2.   What radiation is used in PET scans?
3.       What is ionising radiation?
4.       Give two examples of ionising radiation using in medicine.
5.       State the equation for calculating the intensity of radiation.
6.       State 2 types of non-ionising radiation used in medicine?
7.       Label the diagram of the eye below




8.       What controls the amount of light entering the eye?
9.       What distance is your far point when focussing?
10.   Why does an image get blurred when it is nearer that 25cm to your eye?
11.   What is the job of the ciliary muscle
12.   Where does the image focus in a person who is short sighted?
13.   A person who is long sighted struggles to focus what objects?
14.   What lens shape is needed to correct short sightedness?
15.   What lens shape is needed to correct long sightedness?
16.   How does a converging lens change the path of a light ray?
17.   State methods other than glasses that can be used to correct vision problems.
18.   How can you permanently correct a person’s vision?  Explain how it works.
19.   What is the point at which converging rays meet called?
20.   What are the main causes of short sightedness?
21.   Define the term focal length.
22.   Where is the focal point in a diverging lens
23.   How is the power of a lens measured?
24.   What unit is used to measure the power of a lens.
25.   What is the lens equation?
26.   What factors are linked in the lens equation?
27.   Define a ‘real image’.
28.   Define a ‘virtual image’.
29.   State the law of reflection
30.   What is the ‘normal’?
31.   What is the definition of critical angle?
32.   Give three feature that help to maintain efficient diffusion in the lungs?  Explain how each affects the rate. (6 marks)
33.   How Automatic windscreen wipers work?
34.   What happens to the speed of a wave in denser materials?
35.   When a ray passes into a material where is can move faster does it refract towards or away from the normal?
36.   In Snell’s law what to nr and ni stand for?
37.   Why is a light ray in an optical fibre always reflected back?
38.   What is an endoscope and how does it work?
39.    State 3 ways ultrasound can be used in either diagnosis and treatment

40.   State the 3 main parts of an x-ray machine.
41.   If you increase the potential difference in the machine how does it affect the x-rays?
42.   What is Thermionic emission
43.   Complete the blanks below
Increase temperature = _____________the electrons emitted = ____________ the X-rays produced.

44.   What is inverse square law?
45.   State 2 uses of fluoroscopes
46.   How does a CAT scan work?
47.   Give 2 benefits and 2 risks of X-rays, Fluoroscopes and CAT scans.
48.   How does a pacemaker work?
49.   Define the term action potential.
50.   What 2 things can a pulse oximeter tell us?