Question

A) In which situation did the car achieve the greatest efficiency? (Assume the cars all have the same
mass.) (1 point)
a car that traveled 90 kilometers on 6.0 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 50 kilometers on 4.0 liters of gas

A)
Use the table to answer the question.
Output and Input Work of Different Machines
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)
machine A
machine C
machine D
machine B

A) How does a pulley make work easier when it is used to lift an object? (1 point)
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 reduces the weight of the object being lifted.
It changes the direction of the lifting force to work with gravity.

A) A certain lever system is only 30% efficient. What could make it more efficient? (1 point)
Use a stiffer lever to reduce energy lost bending the lever.
Have more than one person help to lift the lever.
Use it with a lighter load to make it easier.
Make a longer lever that will require less force.

A) What is the efficiency of a ramp if 2,000 joules of energy results in 1,200 joules of work? (1 point)
80%
32%
60%
24%

Answer 1

1) Car efficiency: the one that went 80 km on 5.0 L (16 km/L) — second option.

2) Highest-efficiency machine: machine C (450 J out / 600 J in = 75%).

3) Pulley makes work easier by changing the direction of the lifting force.

4) To make the 30% efficient lever more efficient: use a stiffer lever to reduce energy lost bending the lever.

5) Ramp efficiency: 1,200 J / 2,000 J = 60%.