You are carrying a 7.0-kg bag of groceries as you walk at constant velocity along the sidewalk. You walk a distance of 82 meters
1 answer:
Answer:
0J
Option: B
Explanation:
Work is done when something is moved by the force in the direction of the force. That is the force (e.g., the weight) and the direction the object moves must be aligned for work to be done. In this given condition, the direction is horizontal and the force is downward as its gravity force. That 90° between the two vectors.
The work function is W = m × g ×h × cosθ
Hence,
Work done = 7 × 9.8 × 1.5 × cos(90)
Work done = 0 (cos = 0)
Work done = 0
Therefore work done is 0 J.
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Answer:
D
Explanation:
A) is not correct, because the gravitation potential energy will depend on the height the block is located at. It will be calculated with the formula:
U=mgh.
If we take the ground as a zero height reference, then on point 2 the potential energy will be:
While on point 3, the potential energy will be greater.
B) is not the right answer because the kinetic energy will vary with the height the block is located at in the fact that the energy is conserved (this is if we don't take friction into account or air resistance) so in this case:
We already know the potential energy at point 2. We can calculate the kinetic energy at point 3 like this:
So the kinetic energy at point 2 is given by the equation:
so:
As you may see the kinetic energy at point 2 is greater than the kinetic energy at point 3.
C) Is not correct because according to the first law of thermodinamics, energy is not lost, only transformed. So, since we are not taking into account friction or any other kind of loss, then we can say that the amount of mechanical energy at point 1 is exactly the same as the mechanical energy at point 3.
D) Because of what we talked about on part C, this will be the true situation, because the mechanical energy of the block will be the same no matter theh point you measure it at.