More Physics Clangers


Teachingscienceinallweathers highlights some disappointing Physics errors on the DfE’s National Curriculum documents for Science which have remained uncorrected for over a year (see here, here and here).

This would be bad form on, say, a school website. For an organisation that is in charge of a national education system whose elected leaders do not hesitate to label schools as “coasting” and “lacking rigour”, it is unbelievably shabby and smacks of arrogant, lazy hypocrisy. And these documents are no longer drafts: the DfE website says that “these programmes of study are issued by law; you must follow them unless there’s a good reason not to. All local-authority-maintained schools in England must teach . . . key stage 4 from September 2016.”

Some of the persistent errors highlighted by Teachingscienceinallweathers (and others, including @DrDav, @HRogerson and @miss_m_w) are:

1. The formula for kinetic energy is given as “0.5 x mass x (acceleration)^2” instead of “0.5 x mass x (velocity)^2” [p.37]

2. The formula for weight is given as “gravity force = mass x gravity constant” instead of using the correct scientific terminology of “weight = mass x gravitational field strength”. As Teachingscienceinallweathers points out, the magnitude of gravitational field strength is anything but a “gravity constant”, even near to the Earth’s surface. Similarly, stating that “potential energy = mass x height x gravity constant (g)” [p.37] invites confusion between the constant “big G” the Universal Gravitational Constant (which is genuinely a constant) and “little g” which, as noted above, is not.

3. “Charge flow = current x time” [p.37]: the phrase “charge flow” is confusing in this context. Very often, the phrase “flow of charge” is used as a synonym for “current”. I would argue that “Charge transferred = current x time” would be preferable in this case.

4. “Interpret enclosed areas in distance-time and velocity-time graphs” [p.32]: the area enclosed by a velocity-time graph represents the change in displacement; the area enclosed by a distance-time graph represents . . . erm, nothing with any physical significance, as far as I know.

I would argue that the writers of science examination questions and science specifications have tended towards the prolix over the last two decades, and I, for one, would welcome the return to the more concise but rigorous style of writing of yesteryear when an exam question could begin “A monochromatic ray of light is incident on a plane mirror at an angle of 30 degrees to the normal…” and students were expected to draw an appropriate diagram because the language was clear, formal and unambiguous.

That may indeed have been the intention of the National Curriculum writers, but they are some way from achieving it. In fact, this document is nowhere close.

My own personal bête noire is:

explain with examples that motion in a circular orbit involves constant speed but changing velocity (qualitative only) [p.31]

There is no indication that the writers intend to restrict the meaning of orbit to the celestial sense, and so it seems that it refers to motion on a circular path in general. And therein lies the problem: it might be true in cases where the radius and angular velocity are constant, but the writers do not specify this. Are they considering the motion of an object whirled on a string? Motion in a vertical circle? Motion in a horizontal circle? They don’t say. It is a fair generalisation to say that it is hard to set up motion in a vertical circle that features uniform speed without variable torque to compensate for the transfer of k.e. to g.p.e. and vice versa.

“Explanations of circular motion restricted to examples involving constant speed to introduce the concept of centripetal acceleration as a result of changing direction of velocity” is far from perfect but is, I think, more useful than the original.

In short, those who call for rigour should display rigour.

Weasel Words In Education Part 6: Growth Mindset

It’s taken me a while to realise this, but “Growth Mindset” is essentially the repackaging of that perennial teacher favourite: “Must Try Harder”.

Suppose that the difference in “people who talk up innate ability” and “people who talk up hard work” maps onto a bigger distinction. Some people really want to succeed at a task; other people just care about about clocking in, going through the motions, and saying “I did what I could”.

Put the first group in front of an authoritative-looking scientist, tell them to solve a problem, and make sure they can’t. They’re going to view this as a major humiliation – they were supposed to get a result, and couldn’t. They’ll get very anxious, and of course anxiety impedes performance.

Put the second group in front of an authoritative-looking scientist, and they’ll notice that if they write some stuff that looks vaguely relevant for a few minutes until the scientist calls time, then whatever, they can say they tried and no one can bother them about it. They do exactly this, then demand an ‘A’ for effort. At no point do they experience any anxiety, so their performance isn’t impeded.

Put both groups on their own in private, and neither feels any humiliation, and they both do about equally well.

Now put them in real life. The success-oriented group will investigate how to study most effectively; the busywork-oriented group will try to figure out how many hours of studying they have to put in before other people won’t blame them if they fail, then put in exactly that amount. You’ll find the success-oriented group doing a bit better in school, even though they fail miserably in Dweck-style experiments.
[ . . . ]
So basically, you take the most vulnerable people, set them tasks you know they’ll fail at, then lecture them about how they only failed because of insufficient effort.

Imagine a boot stamping on a human face forever, saying “YOUR PROBLEM IS THAT YOU’RE JUST NOT TRYING NOT TO BE STAMPED ON HARD ENOUGH”.

— Scott Alexander, Slate Star Codex, 8/4/15 [emphasis added]

Recent research shows that children do better in classes where teachers ensure that the region around their cubital ginglymus has a organic epidermal integument attached. Watch this space for more on the Organic Epidermal Integument Elbow Set, next week.

Cubital Ginglymus Organic Epidermal Integument

h/t The Learning Spy, Why The ‘False Growth Mindset’ Reveals So Much

Academisation, Academisation, Academisation

Bogstannard Comprehensive School
Bogstannard Comprehensive School: “Not everybody fails”

MAN IN GLASSES (for it is he): Good evening, viewers. Tonight, we are going to examine the impact of the government’s controversial new education policies ‘on the ground’, so to speak, at one of the first schools in the country to undergo forced academisation in the latest tranche of institutions deemed to be ‘failing’ or ‘coasting’ by Government ministers.


WOMAN: Well, of course, the first we knew about the forced academisation was when the new management team from the SKARO Academy Chain arrived in their shiny new suits.

The new senior leadership team from the SKARO Academy chain arrive…

M.I.G.: And would you say that they’ve succeeded in driving up standards?

WOMAN: A little. The kids are a lot less scruffy since the Headteacher started exterminating anyone who had their top button undone. Or who didn’t know their target grades. Or didn’t make the expected level of progress. Or looked at SLT a bit funny. Mind you, they treated the staff in exactly the same way.

M.I.G: What? You mean that they held staff to the same exceptionally high standards as the children?

WOMAN: No, they exterminated them. Some of the older staff just couldn’t adjust to pushed around on castors with a sink plunger and an egg-whisk under their armpits whilst shouting “YOU WILL MAKE PROGRESS! OR! YOU! WILL! BE! EXTERMINATED!” in a loud, grating voice. But that’s part of the academy chain’s “corporate style” and one of the “non-negotiables”, as the Headteacher likes to call them. But the younger staff seem to be adapting well to new regime, especially those who entered on the SKARO Direct and EXTERMINATE First! routes. Actually, some of them seem to enjoy it . . .


M.I.G.: Have the new leadership team exterminated many of the students?

WOMAN: A fair few. But as Mr Davros, the CEO of SKARO Academy, said in the newsletter, that we shouldn’t think of it as a form of ruthless mass murder, but rather as a “proactive measure to help ease the national pressure on school places”.

M.I.G.:  I understand there was some unpleasantness involving a surprise Ofsted inspection?

WOMAN: Not really. I mean, the lead inspector was a bit suspicious when he found that the majority of the SLT were descended from an extraterrestrial race of humanoids know as the ‘Kaleds’. He said that sounded, well, a bit ‘un-British’ if you catch my drift.

M.I.G.: And what the leadership team do?

WOMAN: Well, two little doors opened up in the dome on top of Mr Davros’ head and two little union jack flags popped out and he started chanting “BRITSH VALUES! BRITSH VALUES! YOU MUST HAVE BRITISH VALUES!” before leading everyone in a rousing rendition of ‘Land of Hope and Glory’.

British values
British values! British values! You must have British values!

M.I.G.: And what happened then?

WOMAN: Oh, they exterminated the Ofsted Lead Inspector.

M.I.G.: Really?

WOMAN: Yeah. He undid his top button while they were singing.

M.I.G.: And how did the staff react to this?

WOMAN:To the Lead Inspector being reduced to a small pile of smoking ashes by an extraterrestrial death ray? Stunned, I think. Followed by some quiet smiles and handshakes and someone saying “I didn’t know we could do that…” Mind you, some of the inspection team didn’t look too displeased either…