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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?
AAll of it
BHalf of it
CNone at all
DTwice as much
Answer & Solution
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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