Post by: cranberry on May 15, 2011, 03:59:42 pm
Question 6
A student celebrating the completion of his examinations takes
an early morning champagne and chicken balloon flight over
Melbourne. At one point in the trip the balloon is rising at a
steady speed of 4.0 m s-1 and is at an altitude of 150 m above the
ground. At this point the unlucky student drops the only bottle
opener in the balloon over the side! Fortunately the champagne
can still be opened.
How long does it take for the bottle opener to reach the ground?
Is 4m/s up, as a constant speed, zero when put into motion equations (as i did below)?
i did:
x=150
u=0
t=?
a=10
and got 5.5s. the answer used u=4 and got 5.9s...does it matter?
ive got a few more which the answers dont explain that well :-\
exam/solutions attached
ty
Post by: Thu Thu Train on May 15, 2011, 04:36:18 pm
Post by: Vincezor on May 15, 2011, 06:39:12 pm
taking 'up' as postive
use quadratic formula
But yes, you must use u=4m/s as the balloon is rising at that speed and the student is in that balloon... so the student is rising at
Post by: cranberry on May 15, 2011, 07:12:55 pm
also this one:
Janette is competing at an athletics track and field meeting
in the high jump.
Janette, who weighs a petite 45 kg, manages to jump a
height of 1.9 metres.
Janette runs towards the bar and pushes off from the ground
at an angle of 80° to the horizontal.
Question 7
What is Janette’s take off speed? (Treat Janette as having projectile motion)
Question 8
How far horizontally has Janette travelled from her take off point when she lands? You can
assume that she lands at the same vertical height that she takes off from.
for Q7 i did:
x=1.9m
a=10
u=?
v=0
using v^2=u^2 + 2ax....idk why they use u
Quote
= U sin 80°i got 6.16m/s (im getting answers just off theirs so idk if my way is right aswell..)
ty
Post by: Vincezor on May 15, 2011, 07:56:57 pm
8.
Horizontally,
However as it is horizontal component, u = v, therefore
So you just find u(horizontal) = ucos80 and T(total) = 2t where t= time taken to reach the top (Time up = Time down)
and just multiply those together to get your answer?
Post by: cranberry on May 15, 2011, 08:17:02 pm