A person is lifting a heavy box using a lever. What is the purpose of the lever in this situation?(1 point)
Responses
to reduce the force needed to lift the box and change the direction of the force
to reduce the force needed to lift the box and change the direction of the force
to reduce the energy needed to lift the box and change the direction of the force
to reduce the energy needed to lift the box and change the direction of the force
to reduce the energy needed to lift the box while keeping the direction of the force the same
to reduce the energy needed to lift the box while keeping the direction of the force the same
to reduce the force needed to lift the box while keeping the direction of the force the same
to reduce the force needed to lift the box while keeping the direction of the force the same
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 70 kilometers on 5.0 liters of gas
a car that traveled 70 kilometers on 5.0 liters of gas
a car that traveled 90 kilometers on 6.0 liters of gas
The car that traveled 70 kilometers on 5.0 liters of gas achieved the greatest efficiency.
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 D
machine D
machine A
machine A
machine C
machine C
machine B
Machine C has the highest efficiency.
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 increases the amount of work produced to lift the object.
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.
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 decreases the distance over which the force must be applied to lift the object.
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.
What is the efficiency of a ramp if 2,000 joules of energy results in 1,200 joules of work?(1 point)
Responses
60%
60%
80%
80%
24%
24%
32%