Answer Key
Simple Machines Pre-test
A. True or False Some questions will change for the test
1. A force is always needed to move something. True
2. Simple machines can help people do work. True
3. The wheel and axle is an example of a complex (or compound) machine. False
4. Friction can be helpful True
5. Machines are used in sports like baseball and hockey. True
6. A pulley is an example of a complex (or compound) machine. False
B. What type of simple machine is used in the following objects. Other examples will be used on the test
Simple Machines: levers, inclined planes, wedges, screws, wheel and axle, pulleys
1. knife Wedge
2. door knob Wheel and Axle
3. propeller on a boat Screw
4. throwing a ball Lever
5. wheelchair ramp Inclined Plane
6. window blind Pulley
C. Place the following items in the middle of the correct class of lever: effort force, load, fulcrum
1. First Class lever Fulcrum
2. Second Class lever Load
3. Third Class lever Effort Force
D. Which type of pulley (fixed, movable, compound) is used to do the following:
1. Change the direction of an effort force and reduce the effort force needed to move a load
Compound
2. Move a load in the same direction as an effort force but reduce the effort force Moveable
3. Change the direction of a force on a load but use the same amount of effort force Fixed
F. Identify the simple machines in this object (if
objects contain a lever, identify the class of
lever and its parts) Two different objects will be
Effort Force |
on the test.
Second Class Lever ~~|
Load ~~|
Different examples will be on the test.
}~~ Fulcrum
Simple machines in this item are:
Lever (second class), screw, wheel and axle
arrows pointing out the location are required on
the test.
Screw |
} Wheel and Axle
C. Sentence answers
1. What is a force? A force is a push or a pull
2.
What is the difference between an inclined plane and a wedge? A wedge often has two
inclined planes back to back and are moved into objects to push them apart. An inclined
plane is stationary and objects are moved on them.
3. If you drop a normal sheet of paper and a lighter, crumpled sheet of paper, which paper will
hit the ground first? Explain why. Wind resistance or friction slows down the open sheet of
paper so it falls slower.
4. What is the difference between a simple and complex (or compound) machine? A complex
or compound machine is made up of more than one simple machine.
5. Why should a screw be considered a complex (or compound) machine? A screw often has a
wedge at the end and is made up of an inclined plane that wraps around a central point.
6.
How are shoe laces pulleys? Fixed pulleys change the direction of an effort force.
7.
Describe how a jar is a simple machine. A jar has a screw top.
8.
How is the front of a ship a wedge? A wedge moves material apart. The front of a ship
moves water away from the front of the ship to allow it to move through the water.
D. Newton's Laws of Motion
1. You are standing on a crowded bus. When the bus comes to a sudden stop, you almost fall
forward. What does this show about motion?
a. Moving objects tend to keep moving.
b. Objects at rest tend to stay at rest.
c. Objects move only when a machine is moving them.
Bonus: Which Newton's law explains the result to question 1: Inertia - every object will remain
at rest or stay moving unless acted upon by a force.
2. When two balls on a pendulum swing down and hit the four balls resting at the bottom of their
swing, what will happen next?
a. All the balls will all swing out a little because only two balls hit them.
b. The swinging balls will bounce back because there are only two swinging balls but four
balls were resting so they are heavier than the two balls.
c. Two balls will swing out from the opposite side of the pendulum because they are the
same weight as the two balls that hit the pendulum.
Bonus: Which Newton's law explains the result to question 2: For every action, there is an
equal and opposite reaction.
3. Why is it more dangerous to jump off the roof of your house than letting go of the monkey
bars in the playground? Gravity keeps pulling at us until we reach the ground. The
greater the distance to the ground, the longer gravity will keep speeding us up and we
will be going fast enough to be hurt when we jump off a roof
Bonus: Which Newton's law explains the result to question 3: Acceleration - As long as a force
is acting on an object it will continue to move faster.