Exampro a-level Physics (7407/7408)

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(ii) 0.87 x (8300 x 9.81 x 140 = 9 917 000) OR V = ✓

= 49 ( = 48.88 ms^-1) ✓
87% of energy for 140m or 160m only for first mark.
Use of 160 (52.26) and / or incorrect or no % (52.4) gets max 1 provided working is shown
Do not credit suvat approaches here
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E1.(a) (i) Most answers referred simply to 'heat and sound'. More detail was expected for full credit. Candidates could have explained where or why heating occurs.

(ii) Many candidates drew an appropriate tangent and used it correctly. Some simply used the data from the final linear portion of the graph. There were many instances of careless reading of graph scales.

There were some who applied equations of motion incorporating the 80 m fallen after leaving the ramp into their calculations.

(iii) The majority of the candidates attempted to equate P.E. to K.E. but the 55% factor was frequently applied incorrectly, yielding a wide range of answers. Some used the equation for uniformly accelerated motion which was not appropriate in this case.

(b) (i) This was often well done. The most common error was to include 23 m s^–1 as an initial vertical speed.

(ii) Allowing errors carried forward many completed this successfully but incorrect answers to (i) produced ski jump distances of up to 500 in!

(c) Surprisingly few took the hint in the stem that momentum change needed to be considered. The expected response was that the skier retains some vertical momentum on impact, reducing the change in momentum and hence, from Ft = ∆(mv), reducing the force. Although such an approach was considered by the more able candidates the thinking of the majority was more muddled. Many took the view that somehow the vertical component of the force was split into a vertical and horizontal component, which consequently reduced the vertical component. Others took the view that vertical momentum was transformed into horizontal momentum.

E6. There were many significant figure errors in the scripts here (the unrounded answer of 12005 J was often quoted as such). Too many candidates thought that they should be carrying out a gravitational potential energy calculation. Use of the wrong value for the change in length of the rope was common too.
Many more candidates scored well here than in part (a) although the wrong value for the change in height was again evident. Some candidates rather curiously subtracted the value determined in part (a) from their (correct) answer. Again significant figure penalties were present and trapped many who had not lost the mark already in part (a).

E7. All but the weakest candidates scored some marks on this question.
In part (a) most candidates who calculated the energy correctly, lost one of the two marks on offer by quoting too many significant figures in their answer.
In part (b) (i), some candidates were penalised for not using their answer from part (a).