Question

A) A person pushes a box. He applies a force of 400 newtons, and he pushes the box for a distance of
4 meters. After he stops pushing, the box slides forward another meter. How much work was done by
the person? (1 point)
400 joules
100 joules
1,600 joules
2,000 joules

A) Which list correctly orders effort (E), fulcrum (F), and load (L) for each lever class? (1 point)
class 1 = L, F, E (or E, F, L)
class 2 = F, L, E (or E, L, F)
class 3 = F, E, L (or L, E, F)

class 1 = F, L, E (or E, L, F)
class 2 = F, E, L (or L, E, F)
class 3 = L, F, E (or E, F, L)

class 1 = F, E, L (or L, E, F)
class 2 = L, F, E (or E, F, L)
class 3 = F, L, E (or E, L, F)

class 1 = F, E, L (or L, E, F)
class 2 = F, L, E (or E, L, F)
class 3 = L, F, E (or E, F, L)

A) How do simple machines make work easier? (1 point)
They decrease the distance needed between a person and an object, allowing the person to apply more
force and do more work.
They magnify the force being applied, thereby decreasing the work they can do with no extra energy
exerted by the person using the machine.
They reduce the amount of force needed to move an object to do the same amount of work.
They increase the distance over which a force is needed, doing more work with less force.


A) A person applies 98 Newtons of force to a 20 kilogram box. They apply the force to the box over a
4-meter ramp, raising the box 2 meters from the ground. How much work is done? (1 point)
40 Joules
80 Joules
392 Joules
194 Joules

A) A person is lifting a heavy box using a lever. What is the purpose of the lever in this situation?
(1 point)
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 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 energy needed to lift the box and change the direction of the force

Answer 1

1) 1,600 joules. (Work = F·d = 400 N × 4 m = 1600 J; the extra 1 m after he stops pushing is not done by his force.)

2) The first list is correct:
class 1 = L, F, E (or E, F, L)
class 2 = F, L, E (or E, L, F)
class 3 = F, E, L (or L, E, F)

3) They reduce the amount of force needed to move an object to do the same amount of work. (Simple machines trade force for distance; work ≈ same ignoring friction.)

4) 392 Joules. (Work = F·d along ramp = 98 N × 4 m = 392 J; equals mgh = 20 kg × 9.8 m/s² × 2 m ≈ 392 J.)

5) to reduce the force needed to lift the box and change the direction of the force.