Question

You carry a 7.0-kg bag of groceries 1.2 m above the ground at constant speed across a 2.7 m room. how much work do you do on the bag in the process?

Answer 1

Since the speed of the bag is constant, it’s kinetic energy remains constant. Since it’s height above the ground is constant, it’s gravitational potential energy is also constant. Since it’s total energy is constant, net work = 0.

Answer 2

Answer:

0 J

Explanation:

Hello,

In this case, as the person is holding the bag and the movement is carried out horizontally, the work is defined via:

$W=Fcos\theta x$

Whereas $W$ accounts for the work, $F$ for the force, $cos\theta$ for the angle between the direction of the movement and the direction of the displacement and $x$ for the displacement magnitude. Considering the above mentioned, one sees that the force is exerted vertically and the movement is carried out horizontally, in such a way, the angle between them is 90° which implies that the work is null since the cosine of 90° is zero no matter the magnitude of neither $F$ nor $x$ as shown below:

$W=Fcos(90) x=0J$

Best regards.