In which condition is no work done:
1. A force pulls an object and speeds it up: When a force is applied to an object in the direction of its motion, causing it to speed up, work is being done on the object. This is because the force is acting in the same direction as the displacement of the object.
2. A force pulls down on an object that moves downward: In this scenario, work is being done on the object. The force is acting in the same direction as the object's displacement, causing work to be done.
3. A force pushes up on an object that stays in place: When a force is applied to an object that doesn't move (stays in place), no work is done. This is because work is defined as the product of the force applied in the direction of motion and the distance the object moves in that direction. If the object doesn't move, then there is no displacement, and hence no work is done.
Therefore, the correct condition where no work is done is when a force pushes up on an object that stays in place.
