Posted on 13 May 2011 at 12:24h

I've just finished doing paper 1 and paper 2 (time zone 2) on my tablet pc so I'll upload them for subscribers later today (Takes a bit of time cropping all the images).

A couple of my students thought the papers were difficult but I always say if the knew it was difficult then that's a good sign, at least they understood the question.

A couple of questions on paper 1 were a bit strange.  didn't like the first one about the uncertainty in speed.

A body accelerates from rest with a uniform acceleration a for time t. The uncertainty in a is x% and the uncertainty in t is y%. The uncertainty in speed is

One would normally calculate the acceleration from the change of speed rather than the other way round so I thought the question meant that the uncertainty in a had been calculated from the uncertainty in speed and time. Anyway the answer you get from that assumption wasn't on offer. maybe I should follow my own advice. "If the going gets tough you've done something wrong".

Another one I wasn't keen on was one about Uranium changing to Plutonium. This takes place by neutron capture followed by beta decay. The answer was neutron capture. I guess most students will have looked at the increase in A and gone for that anyway.

Finally there was a question about tidal power asking how the PE is related to depth. The quick answer is proportional since PE = mgh but on further consideration the mass of water is also proportional to h so PE ∝ h² .

Anyway, it's not easy making up original mc questions so all in all a good effort.

Paper 1 May 2011 Tz2 solutions (for subscribers:-)

Paper 2 May 2011 Tz2 solutions (Unchecked and also for subscribers only)