Space Time & Motion A.3 Work Energy and Power (id: 250167ca1)

本题目来源于试卷: Space Time & Motion A.3 Work Energy and Power，类别为 IB物理学

[单选题]
A motor uses a cable to pull a trolley up an inclined plane at a constant velocity.

Which of the following statements about the energy changes of the trolley during its motion are correct?
Ⅰ.The work done by the engine has greater magnitude than the work done by friction.
Ⅱ.The total of kinetic and potential energy of the trolley increases.

Ⅲ.The gain in gravitational potential energy of the trolley has the same magnitude as the work done by the engine.

A. Ⅰ and II only
B. Ⅰ and III only
C. II and III only
D. Ⅰ, II and III


参考答案:  A


本题详细解析:
Expianation:

Ⅰ： Correct: as the trolley moves up gravitational potential energy increases so work done by the trolley is done against both friction and gravity.

Ⅱ：Correct: kinetic energy is constant since trolley is moving at constant velocity but gravitational potential energy increases as height of it from ground increases.

Ⅲ：Incorrect: some amount of work done by the engine is used to increase gravitational potential energy, but some of it wasted as work done by friction.

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