In which situation did the car achieve the greatest efficiency? (Assume the cars all have the same mass.)(1 point)
Responses
a car that traveled 50 kilometers on 4.0 liters of gas
a car that traveled 50 kilometers on 4.0 liters of gas
a car that traveled 80 kilometers on 5.0 liters of gas
a car that traveled 80 kilometers on 5.0 liters of gas
a car that traveled 90 kilometers on 6.0 liters of gas
a car that traveled 90 kilometers on 6.0 liters of gas
a car that traveled 70 kilometers on 5.0 liters of gas
The car that traveled 90 kilometers on 6.0 liters of gas achieved the greatest efficiency, as it traveled the longest distance while using the least amount of fuel.
Force and Work Unit Test
9 of 129 of 12 Items
Question
Use the table to answer the question.
Machine Output Work (J) Input Work (J)
A 750 1,500
B 1,000 4,000
C 450 600
D 3,000 5,000
Which machine has the highest efficiency?
(1 point)
Responses
machine C
machine C
machine D
machine D
machine B
machine B
machine A
machine A
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To find the efficiency of each machine, we need to calculate the efficiency as the ratio of output work to input work:
- Machine A: Efficiency = Output Work / Input Work = 750 J / 1,500 J = 0.5
- Machine B: Efficiency = Output Work / Input Work = 1,000 J / 4,000 J = 0.25
- Machine C: Efficiency = Output Work / Input Work = 450 J / 600 J = 0.75
- Machine D: Efficiency = Output Work / Input Work = 3,000 J / 5,000 J = 0.6
Therefore, Machine C has the highest efficiency with an efficiency of 0.75.
How does a pulley make work easier when it is used to lift an object?(1 point)
Responses
It changes the direction of the lifting force to work with gravity.
It changes the direction of the lifting force to work with gravity.
It decreases the distance over which the force must be applied to lift the object.
It decreases the distance over which the force must be applied to lift the object.
It reduces the weight of the object being lifted.
It reduces the weight of the object being lifted.
It increases the amount of work produced to lift the object.
It decreases the distance over which the force must be applied to lift the object.
By using a pulley system, the force needed to lift an object is distributed over multiple ropes or pulleys, reducing the distance over which the force must be applied. This makes it easier to lift heavy objects as the force can be spread out and the required distance to lift the object is decreased.
A certain lever system is only 30% efficient. What could make it more efficient? (1 point)
Responses
Have more than one person help to lift the lever.
Have more than one person help to lift the lever.
Use it with a lighter load to make it easier.
Use it with a lighter load to make it easier.
Use a stiffer lever to reduce energy lost bending the lever.
Use a stiffer lever to reduce energy lost bending the lever.
Make a longer lever that will require less force
Use a stiffer lever to reduce energy lost bending the lever.
By using a stiffer lever, less energy is lost due to bending, allowing more of the input work to be used for the intended purpose. This would increase the efficiency of the lever system.
What is the efficiency of a ramp if 2,000 joules of energy results in 1,200 joules of work?(1 point)
Efficiency can be calculated as the ratio of output work divided by input energy, multiplied by 100% to express it as a percentage.
Efficiency = (Output work / Input energy) * 100%
Given:
Output work = 1,200 J
Input energy = 2,000 J
Efficiency = (1,200 J / 2,000 J) * 100%
Efficiency = 0.6 * 100%
Efficiency = 60%
The efficiency of the ramp is 60%.