海綿 asked in 科學其他:科學 · 9 years ago

普物功的問題出自H BENSON 20點!!

P138 1 3 4 6 10

1.True/false:If the kinetic energy of a body is fixed,the net force on it is zero.Explain your response.

3.You lift a box from the floor and place it on a table .Does the amount of work you do on the box depend on how fast you lift??

4.An incline is a sort of machine because it allows us to use a smaller force to accomplish some task.Does this also mean that we do less work?Does the presence or absence of friction affect your answer?

6.If the speed of a car increases by 50% ,by what factor does this increase the stopping distance?

10.Can work be done(a)by the force of static friction,or(b)by a centripetal force?

感激各位大大!!!

1 Answer

Rating
  • msher
    Lv 6
    9 years ago
    Favorite Answer

    1. False

    例如等速率圓周運動, 其動能不變, 但受向心力作用

    3.No

    你對物體所做的總淨功為0, 與你舉起此物的速率無關

    4.No,No

    斜面(或任何機械)可能省力, 但不能省功

    摩擦力出現與否, 不影響結果---不能省功

    6. 摩擦力固定(或近乎固定)

    動能=摩擦力所做的負功大小=摩擦力x 位移

    故動能增加, 位移跟著也變大

    10. (a)No 因淨摩擦力位移為0, 故作功為0

    (b)No 因向心力和(瞬時)位移隨時保持垂直, 故不做功

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