When is negative work done

When a body is falling down, the force of gravitation is acting in the downward direction. The displacement is also in the downward direction. Thus the work done by the gravitational force on the body is positive. Consider the same body being lifted in the upward direction. In this case, the force of gravity is acting in the downward direction. But, the displacement of the body is in the upward direction.

Improve this question. Brandon Enright AndrewChang AndrewChang 1 1 gold badge 1 1 silver badge 3 3 bronze badges. In your example of lowering a box, gravity must be considered. It's not going down that makes a negative work, but, as explained by joshphysics, it's the slowing down of the movement. You can see that what is defined as positive work under one convention is negative work in another. Add a comment. Active Oldest Votes.

Improve this answer. Physics noob here. Is the same true for Quadrant 1? I'm trying and failing to see it. David H David H 1, 10 10 silver badges 16 16 bronze badges. Featured on Meta. Now live: A fully responsive profile. Linked 2. Work: The Scientific Definition Learning Objectives By the end of this section, you will be able to: Explain how an object must be displaced for a force on it to do work. Explain how relative directions of force and displacement determine whether the work done is positive, negative, or zero.

What is Work? Example 1. Conceptual Questions Give an example of something we think of as work in everyday circumstances that is not work in the scientific sense. Is energy transferred or changed in form in your example? If so, explain how this is accomplished without doing work. Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.

Describe a situation in which a force is exerted for a long time but does no work. Express your answer in joules and kilocalories. Find the work done to accomplish this task. Suppose a car travels km at a speed of A gallon of gasoline has 1. Calculate the work done by an See Figure 2. He exerts a force of N on the crate parallel to the ramp and moves at a constant speed.

Be certain to include the work he does on the crate and on his body to get up the ramp. Figure 2. A man pushes a crate up a ramp.