Question

阿蓁

這高中好像有出過，不過有點忘記了QQ

3. A person lifts himself up by hand using the pulley system shown below. “Assume
the total mass of the person and the swing stage is m and the masses of the pulley and
the rope are negligible.。Also, assume there is no frictional force between the pulley
and the rope.(a) What 1s the minimum force, Fmim, applied by the person's left hand
to the rope so that he does not fall down? The person moves up when the applied
force Fis larger than Fmin. “Then, for this F find (b) the acceleration of the person
and (c) the tension in the rope. (d) How much work is done by the person/person's

hand ifthe person goes up, say, by a distance“h””?

  
 

SWling Stage

Ig

物理

Answer 1

✨ 最佳解答 ✨

Sunnyday

把人整個stage取做一個系統，此系統受力只有兩個向上繩張力T和重量mg向下
（a) 問維持不動的最小F？
手給繩子F所以F會等於繩張力大小
2T=mg,T=mg/2=Fmin

(b)
當力為F且大於Fmin,有加速度多少(我下面直接把T用F表示）
2F-mg=ma,a=（2F-mg)/m

(C)tension就等於F

(d)做工等於合力x沿著力方向的位移
h(2F-mg)