Physics MCQs Help.

[Beaconite007]

Please explain the following questions to me.
1) June 2003 Q.20 and 40 (http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s03_qp_1.pdf)
2) June 2005 Q.13 (http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s05_qp_1.pdf)
3) June 2006 Q.9 (http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s06_qp_1.pdf)
4) June 2007 Q.3 and 40 (http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s07_qp_1.pdf)