Considering the definition of work, Marissa must exert a force of 4 N on the window shade.
Work is defined as the force that is applied on a body to move it from one point to another. When a force is applied, an energy transfer occurs. Then it can be said that work is energy in motion.
When a net force is applied to the body or a system and this produces displacement, then that force is said to perform mechanical work. This work can be positive if the system gains energy or negative if the system loses energy.
The work is equal to the product of the force by the distance and by the cosine of the angle that exists between the direction of the force and the direction that travels the point or the object that moves:
Work= Force× distance× cos (angle)
In this case, the angle between the force and the displacement is 0 degrees. This is due to the force and the displacement have the same direction and sense, in the horizontal direction. So the cosine of 0 degrees will have a value of 1. Then, the work is calculated as:
Work= Force× distance× 1
Work=Force× distance
On the other side, you know:
- Work= 3.2 J
- Distance=0.80 m
Replacing in the definition of work:
3.2 J= Force× 0.8 m
Solving:
3.2 J÷ 0.8 m= Force
4 N= Force
In summary, Marissa must exert a force of 4 N on the window shade.
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