Physics MC

(1) 唔知

(2)
條題目應該系漏講 ignore the air resistance，on the whole motion, only gravity force acting on the ball. so the acceleration of the basketball is constant
for(1) v=u+at, v是正比於t和有一個y-intercept，所以correct
for(2)v^2-u^2=2as, 可推到v^2是正比於s但是無y-intercept所以wrong
for(3)s=ut+0.5at^2，s是正比於t^2但是無y-intercept所以wrong

(3)
呢題個圖有D誤導大家，個高度唔可以當2.5和7.5，要當2和7，而a是constant，用反公式v^2-u^2=2as列兩條計算就得


(4)
v^2-u^2=2as
0-(10)^2=2a(25-0.2*10) (因為要計算反應時間在內)
就可以計算答案

v^2-0^2=2(10)(2s)

為什麼不是:
v^2-0^2=2(10)(2x)

thx so much=]

2012-06-27 16:49:59 補充：
thank you very much

Q3:
u=0,a=10,s=2x
v^2-0^2=2(10)(2s)
v^2=40s
s=v^2/40
________________
u=0,a=10,s=7x
(v1)^2-0^2=2(10)(7s)
(v1)^2=140s
s=(v1)^2/140
______________
v^2/40=(v1)^2/140
(v1)=1.87v

2012-06-23 19:24:23 補充：
I type wrong,sorry