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NSC / Matric Energy Transfer in Systems — practice questions

Explore 5 free Energy Transfer in Systems questions in NSC / Matric Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Energy Transfer in Systems questions and exercises with answers

Showing questions 1–5 of 5.

In physics, when is work done on an object by a force?Read the answer and worked solution →A force acts at right angles to the direction in which an object is moving. How much work does that force do?Read the answer and worked solution →A competitor carries two very heavy sleds across level ground at a steady height. How much work does he do on the sleds?Read the answer and worked solution →The net force on an object does work on that object. What must change as a result?Read the answer and worked solution →What is the defining feature of a conservative force?Read the answer and worked solution →

Worked practice questions

In physics, when is work done on an object by a force?

  1. When it acts across the motion
  2. When it acts along the motion
  3. Whenever the object has mass
  4. Whenever the object is heavy
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Correct answer: B. When it acts along the motion

1. Work is the process of transferring energy by means of a force. 2. That transfer needs the object to move while the force acts on it. 3. It also needs part of the force to lie along the line of that movement. 4. So work is done when the force acts in, or against, the direction of the motion. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 5: Work, energy and power_

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A force acts at right angles to the direction in which an object is moving. How much work does that force do?

  1. All of it
  2. Half of it
  3. None at all
  4. Twice as much
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Correct answer: C. None at all

1. Only the part of a force that lies along the motion can transfer energy to the object. 2. A force at right angles to the motion has no part lying along that direction. 3. So a perpendicular force does no work at all, however large it is. 4. This is why the normal force on a sliding block does no work on it. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 5: Work, energy and power_

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A competitor carries two very heavy sleds across level ground at a steady height. How much work does he do on the sleds?

  1. A lot of work
  2. Negative work
  3. Half the work
  4. No work at all
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Correct answer: D. No work at all

1. Everyday language would call carrying heavy sleds very hard work. 2. In physics the test is whether the force has a part along the displacement. 3. His force on the sleds points straight up to balance gravity, while the sleds move sideways. 4. There is no part of his force along the displacement, so he does no work on the sleds. 5. His muscles do use energy to keep the force going, but that energy is not transferred to the sleds, so the answer is not a lot of work. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 5: Work, energy and power_

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