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

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_