physics MCQ...有圖

1. constant resultant force = constant acceleration
(1) 一定岩 , (2) v-t graph with constant slope = constant acceleration 所以岩
(3) 錯 , s-t graph with constant slope = constant velocity => a=0
答案係A

2.離開地面個波就只會有gravitional acceleration 所以答案 = A

3. (1)岩因為舊野冇horizontal acceleration , 所以將T1T2 solve component 之後就證到
(2)岩因為舊野冇vertical acceleration , 同上
(3)岩因為舊野in equilibrium , vector sum of forces acting ot it = 0
=> T1 + T2 = mg (considering magnitude only )
Ans = D

4. 答案是D , A和C是對的 (用上面一題的方法proof)
A式 除 C式 得出 F = x tan (-) 所以 B 是 對的而 D 是錯的

2007-12-26 22:30:07 補充：
睇漏左 X 後面係 kg ....... 所以應該係 D 對 , C錯 , 答案係C

1.A,
(1) by F=ma ,constant a = constant F
(2) slope = a = constant , F constant
(3) slope = v = constant , No resultant Force

2.A 無論甚麼時候,個ball 一離開 cannon 就得番一個force - gravity

3.E
(1,2)cos指左右,sin指上,因為冇net force ,左右一樣 , 上去既force = mg
(3)既然冇net force T1,2 既合力就等如mg

4.C, 好明顯,x 既unit係kg, 不等如force
A - 今次sin係指向上
B - 睇番A , T係constant , 所以F同隻角係正比
D - 10x 即係mg ,mg = T cos = T sin * cot = F cot

(p.s. cot = 1/tan )

希望教到你^^

2007-12-27 19:11:44 補充：
唔好意思,第3題打錯,(1,2,3)都對,是D,解釋冇錯,不過ans打錯

第一題
D
第二題
C
第三題
C
最後一題
B