# Two Oxford Admissions Questions, Pedulums and Aircraft

1. Nov 4, 2008

### alex3

Though I'd scan for ease ;)

1. The problem statement, all variables and given/known data

Check the Pendulum question out here (page 1) and here (page 2),and the aircraft question here.

2. Relevant equations

Should all be in the scans.

3. The attempt at a solution

See the workings scan here.

Aircraft question: a) seems to be obvious to me; travelling at 170km/h, needs to travel 300km. v = d/t, therefore t = d/v = 300/170 = 30/17 hours (no calculator allowed, left it in a fraction). As for b).. Drew a triangle, due north in an hour he should have travelled 170km, due 010 degrees he travelled 134km, but the question's five marks, and I can't think they expect us to know sin or cos of 10 or 80. The thing that really throws me on this question is that his speed is 'relative to the air'.

Pendulum: Got 2π$$\sqrt{\frac{r}{10}}$$, with r being the length of the pedulum. b) I got the same as a), but $$\frac{r}{15}$$. I was thrown on these two because the question said 'calculate', so I assume they want an actual integer, but I couldn't find a hint in the question to what r should be to substitute. c) was harder. Could not quite understand the question enough to answer it. d) seemed ok, I ended up with a messy fraction (right at the bottom of the workings scan) and thought I must have buggered up the algebra some where. e) would've probably have been fine if I got d).

I just need pointing in the right direction; it's more getting my head thinking along the right lines than getting the exact integer if required (though that'd be nice!) Thanks!

Last edited: Nov 4, 2008
2. Nov 4, 2008

### alex3

I'm really sorry for bumping this, I know how irritating it is but I have this test tomorrow, and I know knowing these exact answer won't help for it but I'd like to get my head around the thinking.. :)

3. Nov 6, 2008

### alex3

The aircraft one I have done. Draw a line to show how far he would have travelled in one hour due North, and then the line bearing 10 degrees. Join these two up. You've got two sides and an angle, so cosine rule.

I've done the test now, but I'm still curious about the pendulum one. Any takers?