Answer:
The girl is doing work on the ball because the energy in her muscles changed, even though the ball is not displaced.
Explanation:
The complete question is...
Which of these correctly describes whether a girl holding a ball in the same position is doing work on the ball?
-The girl is doing work on the ball because the energy of the ball changed, even though it is not displaced.
-The girl is doing work on the ball because the energy in her muscles changed, even though the ball is not displaced.
-The girl is doing no work on the ball because the ball is not displaced.
-The girl is doing no work on the ball because she is exerting a net force on the ball.
Holding up a ball costs energy, which is used to counter the work that would have otherwise be done on the ball by gravity. Although no physical distance is moved, we should consider the fact that by holding the ball, the girls hand exerts physical force to hold the ball in place. Also, there is a potential gravitational work on the ball due to gravity, but the force exerted by the girls hand does an equivalent of this gravito-potential work in order to counter it and hold the ball in place. All these activities eventually lead to a change in energy in her hand muscle to show that energy is expended.
A would be the answer because thats how long it takes
The average angular acceleration of the fan is
The number of revolutions after time is given by
Acceleration is assumed to be constant, so and over the 2 second interval we have
so the answer is A.
Answer:A force can be described as a push or a pull. Pushes and pulls can be seen to act on objects when they begin to move, speed up, slow down or change direction.
The image gallery on this page shows children at play using push and pull actions to move objects. Children use push and pull all the time while at play. While playing, students learn to manipulate objects and materials and make observations about their actions.
Teachers may use this teaching resource over a number of lessons to explore and develop their students' understanding that a push or a pull affects how an object moves or changes shape.
Explanation: