You must raise the weight to a height of 10 meters. You cannot do it! Thinking back to what you have learned in science class, y
ou set up the pulley you see here. How does using this pulley reduce the force needed to lift the weight 10 meters?
2 answers:
A single pulley has no advantage in reducing force. A single pulley only helps by changing direction of effort, pulling something from up to down feels easier then vice versa due to our muscles arrangement. However, the force needed is the same.
Meanwhile multiple pullies divide the tension. The lower pulley itself reduces the force into half so as to you feel a part of the tension while rest is suspended by the ceiling in the case in the diagram below.
Meanwhile multiple pullies divide the tension. The lower pulley itself reduces the force into half so as to you feel a part of the tension while rest is suspended by the ceiling in the case in the diagram below.
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Answer:
d. Potential energy is converted to kinetic energy; the kinetic energy is then converted into the work of bringing the body to a stop.
Explanation:
- At the beginning of the falls, when the person is still at a certain height h, the person has gravitational potential energy:
U = mgh
where m is the mass of the person, g the acceleration due to gravity, h the height above the ground.
- As the person falls down, h decreases, so the potential energy decreases; according to the law of conservation of energy, potential energy is converted into kinetic energy, since the speed of the person increases:
where v is the speed.
- Just before hitting the ground, all the potential energy has been converted into kinetic energy
- When the person hits the ground, he/she comes to a stop: so work is done by the ground on the person, because the ground applied a force required to stop the person, and the kinetic energy "lost" by the person is equal to the work done by the ground to bring the body to a stop.