Question

我不行了

請問有人會這兩題嗎

考題精選
(0)
1. 右圖為直線運動之加速度對時間之關係圖,若物體初速度為0,請問第一
秒內,第二秒內,第三秒內之位移比為下列何者?
(A)1:1:1 (B)1:2:3 (C)1:3:5 (D)1:4:9 (E)1:7:19。
【答】(E)
a
2. 如右圖所示,三塊完全相同的木塊固定在地板上,
一初速為Vo的子彈水平射穿第三塊木板後,速度
恰好為零。設木板對子彈的阻力不隨子彈的速度而
變化,求子彈依序穿過木塊前的瞬時速度比為
VO
2
3
(A)4:2:1 (B)3:2:1 (C)2: 3:2(D)2:2:1(E)3:2:10
【答】(E)

Answer 1

Tomato

1. use the formula: x=(1/2)at^2.
note that 第一秒內is the distance traveled from t=0 to t=1.
2. the work done by friction is the same for the three blocks, given that the friction does not vary by the bullet's speed.
Also, we know that work done by friction = loss in kinetic energy.->kinetic energy loss is the same in the three blocks...