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Question 1 A)Which is the equation for a machine’s efficiency?(1 point) Responses Efficiency=input energyoutput energy ⋅ 100Efficiency=input energyoutput energy · 100Efficiency=input energyoutput energy ⋅ 100Efficiency=input energyoutput energy · 100 Efficiency=input energy+output energyEfficiency=input energy+output energyEfficiency=input energy+output energyEfficiency=input energy+output energy Efficiency=input energy−output energyEfficiency=input energy−output energyEfficiency=input energy−output energyEfficiency=input energy−output energy Efficiency=output energyinput energy . 100Efficiency=output energyinput energy . 100Efficiency=output energyinput energy . 100Efficiency=output energyinput energy . 100 Question 2 A)A rotating space heater used 1,400 joules of energy while heating a room. Of that total, 896 joules produced thermal energy, 181 joules produced kinetic energy, 203 joules produced light energy, and 120 joules produced sound energy. What is the space heater’s efficiency?(1 point) Responses 36% 36% 64% 64% 56.25% 56.25% 156.25% 156.25% Question 3 A)Lenore is on an inclined plane next to her truck. Holding her hands steady, she pushes a box up the plane and into her truck. Where can energy be lost?(1 point) Responses Friction between Lenore and the ground. Friction between Lenore and the ground. Friction between Lenore’s hands and the box. Friction between Lenore’s hands and the box. Friction between the box and the inclined plane. Friction between the box and the inclined plane. Friction between the truck and the inclined plane. Friction between the truck and the inclined plane. Question 4 A)Ronald pushes a box up an inclined plane with 35% efficiency. If 224 joules of energy went into moving the box, how much energy did Ronald put into the inclined plane?(1 point) Responses 145.6 joules 145.6 joules 640 joules 640 joules 189 joules 189 joules 78.4 joules 78.4 joules Question 5 A)1000 joules of energy are put into a pulley system, and 400 joules come out. What does the Law of Conservation of Energy imply about the lost energy?(1 point) Responses The pulley system could be improved to conserve some of the lost energy. The pulley system could be improved to conserve some of the lost energy. The lost energy cannot be recovered. The lost energy cannot be recovered. The lost energy is not truly lost, but it changed into a different form. The lost energy is not truly lost, but it changed into a different form. The lost energy is caused by friction. The lost energy is caused by friction.

1 answer

Here are the answers to your questions:

Question 1: A) Which is the equation for a machine’s efficiency?

  • Correct response: Efficiency = (output energy / input energy) · 100

Question 2: A) A rotating space heater used 1,400 joules of energy while heating a room. The total output energy produced was 896 joules (thermal energy) + 181 joules (kinetic energy) + 203 joules (light energy) + 120 joules (sound energy) = 1,400 joules.

  • Total output energy = 1,400 joules.
  • Efficiency = (output energy / input energy) · 100 = (1,400 / 1,400) · 100 = 100% (Note: Based on the energy breakdown mentioned, the efficiency is essentially 100%, but you may want to clarify if you're being asked about usable output only or if some energy is lost in the context of this question).
  • Potential correct response: 100% (but since this option is not present, I recommend considering which output energy is useful for heating).

Question 3: A) Where can energy be lost when Lenore pushes the box up the inclined plane?

  • Correct response: Friction between the box and the inclined plane.

Question 4: A) Ronald pushes a box up an inclined plane with 35% efficiency. If 224 joules of energy went into moving the box, how much energy did Ronald put into the inclined plane?

  • Energy output = 224 joules
  • Efficiency = 35%
  • Input energy = Output energy / Efficiency = 224 joules / 0.35 = 640 joules
  • Correct response: 640 joules.

Question 5: A) If 1000 joules of energy are put into a pulley system, and 400 joules come out, what does the Law of Conservation of Energy imply about the lost energy?

  • Correct response: The lost energy is not truly lost, but it changed into a different form.

Let me know if you need further clarification!