Paper 4 October/November 2008 MATHEMATICH (9709/4) A Levels
لطفا برای اطمینان از عملکرد و تجربه بهتر از مرورگرهای مدرن و به روز مانند کروم یا فایرفاکس استفاده کنید.

Particles $P$ and $Q$ are projected vertically upwards, from different points on horizontal ground, with velocities of $20{\text{ }}m{\text{ }}{s^{ - 1}}$ and $25{\text{ }}m{\text{ }}{s^{ - 1}}$ respectively. $Q$ is projected $0.4{\text{ }}s$ later than $P$. Find
a) the time for which P’s height above the ground is greater than $15{\text{ }}m$,
b) the velocities of $P$ and $Q$ at the instant when the particles are at the same height.