first of all, put any gaming consoles in the cupboard!
if you can't study because you're thinking there's too much to do (e.g. doing a full three hour practice maths paper) then break down your work into smaller tasks (e.g. start by doing questions 1 and 2 for the last few hscs and check your...
If initial velocity is 80m/s:
u(h)=80cos45
u(v)=80sin45
range = u(h) x t(v)
150 = 80cos45 x t(v)
t(v) = 2.65 s
r= ut + 0.5at^2
= 80sin45 x 2.65 + .5 x -9.8 x 2.65^2
= 115.5 m
hope that makes sense
I have no idea about question 1 either.
I got an answer for question 2, although it involves simultaneous equations and a trigonemetric property i just learnt about in 3 unit maths (*), so there must be an easier way.
(Let # be the angle we have to find)
u = 30m/s
u(horizontal) =...
You assumed that upwards was positive, since you said displacement = -10m and acceleration due to gravity is -9.8ms-2. But then wouldn't the downwards (i.e. vertical) velocity have to be negative as well? (i.e. -7.5ms-1)
then
-10= -7.5t-4.9t2
4.9t2+7.5t-10=0
Using the quadratic forumla...
isn't distance supposed to be 0.15m (=15cm) rather than 0.015m (=1.5cm)?
r=ut+.5at^2
0.15 = 0 + .5 x -9.8 x t^2
t = 0.17s
r=ut
250=u x 0.17
u=1428.87 m/s (i only started yr 12 as well, so i could be wrong too)